Formative Quiz Review 1

Question 1

A 4-year-old child is referred to you with the diagnosis of leukocyte adhesion defect. She has a history of recurrent bacterial infections, including pneumonias and skin abscesses. Radiography demonstrates granuloma-like lesions in her lungs and liver. However, the data in Table 1 suggests this condition has not been properly diagnosed. Which one of the following elements of these data is INCONSISTENT with a diagnosis of LAD?

CD2 values

CD19 values

CD18 values

CD4 values

CD3 values

Answer 1

CD 18 values - C. Correct. Leukocyte adhesion defect is an absence of LFA-1, CR3 and CR4. CD11a is a component of one of these receptors (LFA-1) and its expression is altered in these patients. CD11a pairs with CD18 to form the LFA-1 receptor. Because the actual defect in LAD is the absence of CD18, any receptor that uses CD18 would be absent from LAD cells. In this patient, the normal numbers of CD18-positive cells also indicate that she has been misdiagnosed.

Question 2

A patient arrives at a clinic with a number of boils on his back, and a sample of pus from one of the lesions was sent to the laboratory for culture. The microbiology laboratory cultures heavy growth of Staphylococcus aureus, a gram-positive bacterium. Which of the following innate immune components is probably NOT involved in the protective response to this pathogen?

C5a

C3b

Superoxide

Lysozyme

TLR4

Answer 2

TLR 4 - LPS is not present in gram-positive bacteria.

Question 3

The cartoon of the portly mouse below depicts the vascular and lymphatic systems, showing a T cell that will travel through both duct systems. Which of the following best represents the path taken by a naïve T cell?

Aorta, Heart, Lung, Lymphatic vessel, Gut, Lymph node, Aorta

Aorta, Spleen, Heart, Aorta, Lymph node, Lymphatic vessel, Heart, Lung, Aorta

The T cell is most likely to remain in the blood stream only, as there is no antigenic challenge.

Aorta, spleen OR lymph node; the T cell will remain at one of these secondary lymphoid structures until it encounters antigen.

Answer 3

Aorta, Spleen, Heart, Aorta, Lymph node, Lymphatic vessel, Heart, Lung, Aorta - T cells travel through the blood stream to gain access to the secondary lymphoid structures, where they reside and ‘travel’ for a short time in search of antigen. If they do not encounter antigen (Question 4) within the lymphoid structure they exit via the draining veins (spleen) or efferent lymphatic ducts (lymph nodes), recirculate by making their way back to the heart where they begin their journey once again.

Question 4

The neutrophils (N) in the accompanying photomicrograph are attracted to their extravascular location primarily by which one of the following factors?

C3a

C5a

C5b

Collagen

Fibrin

Neutrophil chemotactic factor

Answer 4

C5a - Neutrophils follow a gradient formed by complement factor C5a to the site of injury. Other factors may also be involved, including certain bacterial peptides, but C5a is the most widely known and understood

Question 5

TAP is a component of which MHC pathway?

Answer 5

MHC class I pathway

Question 6

Polymorphisms in HLA-A are most likely to influence the affinity of the interaction between which of the following pairs:

HLA-A and anchor residues

HLA and ß2m

HLA-A and CD8

HLA-A and chaperones

HLA and TAP

Answer 6

HLA-A and anchor residues - polymorphisms in HLA influence the ability of HLA to bind peptides and the TCR. The amino acids of the peptides that associate with HLA are called anchor residues.

Question 7

You are characterizing the macrophage response to the bacterium Pseudomonas aeruoginosa. Knowing that this gram-negative bacterium has a potent endotoxin, you decide to determine if IL-1 transcription is activated by the pathogen through a Toll-like receptor. Which of the following signaling intermediates is involved in this pathway?

IκB

NFAT

NOD

PLCγ

Stat-1

Answer 7

IkB

Question 8

Which one of the following is a “pattern recognition receptor” of the innate immune system that can distinguish host and microbial structures?

• Fc receptor
• Complement receptor 3 (CR3)
• Toll-like receptor 9 (TLR9)
• α-defensin
• BCR

Answer 8

Toll-like receptor 9 - Correct. Toll-like receptors are good examples of receptors capable of recognizing molecular patterns on microbes and distinguishing them form host structures.

Question 9

Which one of the following processes contributes most to the increase in affinity of an antibody response over time (affinity maturation), especially following multiple immunizations?

Somatic hypermutation

BCR editing

Ig class switching

Joining of V, D and J segments in memory B cells

Activation of Th1 cells

Answer 9

Somatic hypermutation - Affinity maturation is the process by which an animal’s antibody response over time acquires a higher average affinity. This results from the selective activation of B cells that bear antigen receptors (BCR) with high affinity for the immunizing antigen. Somatic hypermutation occurs during memory B cell development and generates mutated BCR, some with much higher affinities for the antigen.

Question 10

Recently, a patient was described who had a defect in TLR4-initiated cell signaling. Which of the following groups of microbes would be expected to cause recurrent infections in this patient?

Respiratory viruses

Fungi that cause vaginal yeast infections

Gram-negative bacteria

Gram-positive bacteria

Insect vector-borne parasites

Answer 10

Gram-negative bacteria - Toll-like receptor 4 (TLR4) is a member of receptors that recognize conserved microbial components and initiate innate immune responses. TLR4 is a specific signaling receptor for the lipopolysaccharides (LPS) found on gram-negative bacteria. It is not known to bind to fungal, viral or parasitic ligand.

Question 11

Which one of the following properties would distinguish (be different between) IgG and IgM antibody molecules?

Their ability to activate complement

Their ability to bind to human mast cell Fc receptors

Their presence of κ light chains

Their ability to cross the placenta

Their ability to precipitate soluble antigens

Answer 11

Only human IgG can cross the placenta; IgM cannot.

Question 12

Which one of the following properties of the complement system requires the terminal components, including C9?

Chemotaxis

Inflammation

Membrane attack (lysis)

Opsonization

Recognitition of microbes

Answer 12

Membrane attack - lysis

Question 13

Which one of the following cytotoxic cells is most active against host cells that DO NOT express MHC class I molecules?

Cytotoxic T cells

Natural killer cells

Natural killer T cells

Neutrophil

Macrophage

Answer 13

NK cells bear an inhibitory receptor for MHC class I molecules that keeps the NK cells quiescent in the presence of class I molecules. In cells that lack class I expression (e.g., tumor cells or virus-infected cells), the inhibitory receptor is not engaged allowing the NK cell to become activated.

Question 14

An immune-deficient patient is diagnosed with a congenital defect in RAG-2 expression. Which
of the following observations would MOST LIKELY be seen in this patient?

Aberrant B cell development in the thymus

A lack of peripheral B cells, T cells, and NK cells

An absence of double positive and single positive thymocytes

Normal peripheral B cell numbers and a lack of CD4+ T cells

Normal peripheral CD4+ T cell numbers and a lack of B cells

Answer 14

An absence of double positive and single positive thymocytes - RAG is required for the rearrangement of genes that encode the BCR and TCR. Cells of the B and T cell lineages dependent on expression of a pre-BCR or pre-TCR would be absent or extremely low. This includes any cell beyond the pre-B stage or the DN stage.

Question 15

In which of the following infectious diseases is a Th1 pattern of cytokine production the most beneficial?

E. coli urinary tract infections

Tuberculosis

Streptococcal pneumonia

Pseudomonas-associated sepsis

Staphylococcal skin infections

Answer 15

Tuberculosis - Th1 cytokines, such as IFN-g, are important against intracellular bacterial pathogens, such as M. tuberculosis, the causative agent of tuberculosis. IFN-g serves to activate infected macrophages for bacteriocydal activity.

Question 16

Mixed lymphocyte reaction does what?

Answer 16

C. The MLR is used to measure HLA incompatibility between two individuals.

Question 17

Approximately how many Ig gene segments are required to produce antibodies with 1 billion different specificities?

1 billion

1 million

10

100 million

100

Answer 17

100

Question 18

VLA-4 binds?

Answer 18

VCAM-1

Question 19

The image below depicts a portion of the Peyer’s Patches of the small intestine. Match the following functions with the letters that appear in the photomicrograph. Note that for clarity, some duplicate structures are labeled with the same letters. The location of the cells responsible for initial antigen uptake is:

Answer 19

D - villi

Question 20

ABO blood antigens are:

Answer 20

Carbohydrates

Question 21

Anaergy is a form of central or peripheral tolerance?

Answer 21

Both Central and Peripheral

Question 22

What is the role of CR3?

Answer 22

The CR3 receptor binds Ag-Ab-iC3b complexes, and CR3 and CR4 are expressed on neutrophils and monocytes,

Question 23

The ligand for this cell surface receptor requires TAP for its expression. Which of the following is the cell surface receptor?

CD3

CD8

CD18

CD19

CD154

Answer 23

CD8 - CD8 binds to MHC class I molecules, which require the transporter of antigenic peptides (TAP) for their expression.

Question 24

Which of the following processes contributes the most to the size of the repertoire of T cell antigen receptors of an individual?

DNA recombination

Large pools of V region genes

Somatic hypermutation

Polymorphism

Active immunization

Answer 24

DNA recombination - Recombination of the V, D, and J regions accounts leads to the production of 10^9 unique B and T cell clones.

Question 25

At which one of the following stages of B cell differentiation does Bruton’s tyrosine kinase (Btk) first play an essential role? Plasma cell Memory B cell Mature B cell Immature B cell Pre-B cell

Answer 25

Pre-B cell - Precursor (Pre-) B cells are the first step in the B cell lineage that requires Btk for their maturation. This is evidence by deleting the gene in experimental animals or by studying XLA patients who lack a functional Btk. They do not show B cell lymphopoiesis beyond the pre-B cell stage.

Question 26

An analysis of the blood lymphocyte subsets of an adult individual with a defect in his cell-mediated immunity was performed. Which one of the flow cytometry results shown in the figure below is consistent with a TAP deficiency in this patient?

Answer 26

D - This is a normal pattern for blood lymphocytes, except for the absence of CD8+ T cells. With a TAP deficiency, the patient does not express MHC class I molecules and does not develop the CD8+ subset because of the lack of positive selection in the thymus.

Question 27

Which of the following is a mechanism that regulates the size of the MHC class I repertoire within an individual: Vd.J recombination Each cell expresses two allelic forms of MHC class I Forming dimers with different combinations of a and b genes Somatic hypermutation of MHC class I genes Different cell types express different allelic forms of MHC class I

Answer 27

Each cell expresses two allelic forms of MHC class I

Question 28

Inducible Cox-2 activity functions in a pro-inflammatory pathway by?

Answer 28

catalyzing prostanoid production in fibroblasts and macrophages

Question 29

Which of the following is one of the most common causes of neutrophilia? Parasitic infections Chemotherapy for cancer Bacterial infections HIV/AIDS Exposure to ionizing radiation

Answer 29

Bacterial infections - Elevated WBC counts should always suggest an infection. Parasitic infections more often induce eosinophilia; chemotherapy generally produces neutrophenia; HIV results in lymphopenia; and radiation exposure can cause pancytopenia.

Question 30

Cytotoxic T lymphocytes can use multiple mechanisms to kill target cells. These include: Expression of Fas ligand and release of granzymes. Detection of loss of MHCII from the cell surface. Detection of loss of MHCI from the cell surface. Production of reactive oxygen and nitrogen intermediates. Generation of complement, and hydrolases that can attack and destroy cells.

Answer 30

Expression of Fas ligand and release of granzymes. ​

Question 31

Which one of the following is an immune evasion property of encapsulated bacteria, such as the pneumococcus? Resistance to antibody binding Resistance to antimicrobial peptides Resistance to complement activation Resistance to phagocytosis Resistance to oxidants

Answer 31

Resistance to phagocytosis

Question 32

Which one of the following is a property of peptides presented on MHC class II molecules? They maintain their native conformation. They are generated by proteasomes. They bind β2-microglobulin. They are derived from extracellular proteins. They are transported by TAP.

Answer 32

They are derived from extracellular proteins. - Peptide antigens that bind to the class II MHC molecules are processed through the exogenous class II pathway by which extracellullar proteins are internalized within endosomes within the antigen-presenting cell.

Question 33

Figure #1 illustrates a family pedigree in which HLA genotypes are shown. Which of the five children shown here is the child of a previous marriage involving the mother?

Answer 33

Daughter 2 - This daughter has apparently inherited her A1+ B32 haplotype from her mother. That leaves A1 + B3 from her biological father, which is not a haplotype she could have received from the father that is shown here. Thus, her genetic father is not shown and she is therefore a daughter of a previous marriage with the mother shown here.

Question 34

With which of the following regions of MHC molecules can the T cell receptor on CD8+ T cells interact? ## Footnote α1 and α2 α1 and β1 α1 and β2m α2 and α3 α2 and β2m

Answer 34

α1 and α2 ​

Question 35

A mouse is injected with an antigen that elicits an immune response that is characterized by a predominance of IgM production, no somatic hypermutation, and no memory formation. Which of the following properties MOST likely characterizes the antigen? The antigen can be presented by MHC class II. The antigen can bind both BCRs and TLRs. The antigen can induce cell-mediated immunity. The antigen can induce IL-13 production. The antigen can inhibit Th17 differentiation.

Answer 35

The antigen can bind both BCRs and TLRs. - An antigen that induces an immune response with these characteristics is most likely a T-independent antigen. TI antigens are patterns and can also activate pattern recognition receptors, such as TLRs.

Question 36

From analysis of the accompanying high power photograph, how would you classify the acute inflammatory exudates seen? ## Footnote Eosinophilic Fibrinous Fibrous Granulomatous Purulent

Answer 36

**Purulent - The photomicrograph shows an abundance of neutrophils** (N). By definition, this is a purulent or suppurative exudate. This is the typical pattern of acute inflammation when the inciting stimulus is a pyogenic (pus forming) bacterial infection.

Question 37

Which of the following is a mechanism that determines the size of the MHC class I repertoire within an individual? Different cell types express different allelic forms of MHC class I Each cell expresses two allelic forms of MHC class I in a codominant fashion Forming dimers with different combinations of α and β genes Somatic hypermutation of MHC class I genes Vd.J recombination

Answer 37

Each cell expresses two allelic forms of MHC class I in a codominant fashion

Question 38

Which of the following cells of the small intestine produces secretory component that is found in secretory IgA?

Answer 38

epithelial cells

Question 39

Plasma cells are primarily responsible for which one of the following physiologic functions? * Antibody production * Collagen production * Cytokine production * Non-specific killing of invading bacteria * Ingestion of dead or damaged tissue

Answer 39

Antibody production - Plasma cells are responsible for antibody production, which can result in the specific killing of bacteria. Non-specific killing is done by the neutrophils, via their myeloperoxidase system. Cytokines are largely produced by lymphocytes and macrophages.

Question 40

The T cell antigen receptor signals through several intracellular biochemical pathways. Which of the following T cell receptor-mediated events is inhibited by cyclosporin? The phosphorylation of IκB The phosphorylation of ITAM motifs The dephosphorylation of cytosolic NF-AT The recruitment of ZAP-70 The phosphorylation of CD3ζ

Answer 40

The dephosphorylation of cytosolic NF-AT - NF-AT exists as a phosphorylated protein in the cytosol in resting cells. Cell activation results in the activation of a calcium/calmodulin-dependent phosphatase, called calcineurin, which dephosphorylates NF-AT. The dephosphorylated NF-AT can then move to the nucleus where it activates transcription. Cyclosporin blocks the activity of calcineurin and, therefore, blocks NF-AT-dependent transcription.

Question 41

Mice have been genetically engineered so that they do not express the β2-microglobulin gene (β2-microglobulin knockouts). What effect would this mutation have on lymphocyte differentiation? The mutants would not produce a population of CD4 CD8 thymocytes The mutants would show reduced numbers of CD8 cells in their lymph nodes. The mutants would have a phenotype similar to CD3 knockouts. The mutants would have defective NK cell function. The mutants would have defective Th1 cell function.

Answer 41

The mutants would show reduced numbers of CD8 cells in their lymph nodes. - The absence of β2-microglobulin would prevent MHC class I expression, which would prevent positive selection of single-positive CD8+ thymocytes. This would leave the animal without peripheral CD8+ T cells as well.

Question 42

Does class switching occur in the T cell lineage?

Answer 42

NO

Question 43

An otherwise healthy 26 year-old woman has a small laceration on her forearm. Microorganisms from the skin flora enter the wound and are captured by the Langerhans cells. Which of the following is the primary function of these Langerhans cells? * Migrate to the cortex of the lymph node and present antigen to B cells via FcγR. * Migrate to the paracortex of the lymph node and present antigens to T cells via MHC. * Secrete IL-1 and induce the fever response. * Secrete IL-4 and induce class-switch recombination. * Release reactive oxygen species and destroy the pathogens.

Answer 43

Migrate to the paracortex of the lymph node and present antigens to T cells via MHC. - Langerhans cells are intradermal dendritic cells that present antigens to T cells. When activated by pathogens, Langerhans cells express chemokine receptors that induce migration into the T cell zone of lymph nodes.

Question 44

Hematopoiesis is a process that is tightly regulated by cytokines. Which of the following cytokines regulates myelopoiesis, but not lymphopoiesis? G-CSF IL-2 IL-3 IL-7 IL-15

Answer 44

G-CSF

Question 45

Neoplastic cells were prepared from a lymph node biopsy obtained from a patient with a lymphoma. The cells are analyzed by flow cytometry and the following phenotype is reported: CD3: negative CD19: positive Intracellular Ig μ heavy chain: positive Intracellular Ig κ and λ light chains: negative From which of the following stages of lymphocyte development is this tumor most likely derived?

Answer 45

Pre-B cells - This phenotype indicates the B lymphoma cells were derived from pre-B cells, which express heavy mu chains, but no light chain. CD19 is a pan marker for B cells.

Question 46

A 35-year-old man with a history of abdominal pain associated with edema affecting the bowel wall presents with an acute onset of nonpruritic facial edema. He has no history of allergies, and skin tests in the past have always failed to detect atopic allergies. Analysis of his serum complement shows decreased C2 and C4. Of the following treatments, which is the most appropriate for his current condition? ## Footnote Recombinant IL-2 Recombinant C4 Recombinant C1 Inhibitor Anti-IgE Epinephrine

Answer 46

**Recombinant C1 inhibitor** - Giving more complement components may exacerbate this patient’s condition. The absence of hives and positive skin tests suggests that IgE antibody is not involved, do epinephrine is not likely to be beneficial. **The condition is consistent with HAE, a condition we treat with recombinant C1 Inh.**

Question 47

Which of the following complement components inactivates the C3 convertase without altering the ability of C3 peptides to act as opsonins? C3a inactivator Factor I Factor B C1 inhibitor Factor D

Answer 47

Factor I - Factor I converts C3b and C4b into iC3b and iC4b, respectively. **These inactivated peptides retain the ability to bind CR3, but no longer can form C3 or C5 convertases.**

Question 48

Parents of a lost child arrive at mall security in a panic. At the same time, five lost children arrive at mall security. The security officer performs a quick blood test to determine which child belongs with these parents. Which of the following children are most likely these parent’s child? HLA-A2, A4, HLA-B8, B1, HLA-DR2, DR3 HLA-A2, A4, HLA-B2, B1, HLA-DR3, DR1 HLA-A2, A5, HLA-B8, B2, HLA-DR2, DR6 HLA-A4, A10, HLA-B8, B1, HLA-DR1, DR3 HLA-A2, A5, HLA-B8, B2, HLA-DR2, DR1

Answer 48

HLA-A2, A4, HLA-B8, B1, HLA-DR2, DR3

Question 49

A patient is diagnosed with a deficiency in the expression of the CD18 integrin. Which one of the following would you expect to be abnormal in this patient? Binding of iC3b by neutrophils Activation of the alternative pathway of complement Production of TNF-α by macrophages in response to LPS Activation of macrophages by IFN-γ Activation of B cells in response to protein antigens

Answer 49

Binding of iC3b by neutrophils - A. Correct. CD18 is one member of the dimeric family of β 2 integrins. These are cell surface receptors that mediate cell adhesion and complement component binding. CD18 pairs with either CD11a, CD11b or CD11c to form LFA-1, CR3 or CR4, respectively. Thus, a mutation in CD18 will impair the function of three different cell surface receptors. The ligands for LFA-1 are ICAM-1, which facilitates leukocyte adhesion to endothelial cells. CR3 and CR4 bind iC3b, which promotes opsonophagocytosis of immune complexes that are coated with the complement component. This disease is called leukocyte adhesion defect-1 (LAD-1). The leukocytes of these patients do not bind iC3b well, but show normal complement activation, cytokine production and recognition of protein antigens. Thus, LAD patients suffer from two host defense problems: they do not extravasate leukocytes to sites of infection and they do not cannot use complement as an opsonophagocytic agent.

Question 50

Quantitative test of immunoglobulins

Answer 50

This test measures the concentration of the five immunoglobulin isotypes in an unknown sample (e.g., serum).

Question 51

The neutrophils (N) in the accompanying photomicrograph are arranged at the peripheral wall of the blood vessel shown. Which one of the following is CORRECT regarding their orientation in relation to the blood vessel? ## Footnote Extravascular Marginated Mid-axial Neutrophils should not be present in peripheral blood Normal

Answer 51

Marginated - The neutrophils have marginated, due to the presence of selectins and chemotactic factors, which attract them to the site of injury. Normally, neutrophils assume a mid-axial location. Inflammation dilates the vessel and slows flow, allowing margination and exudation through the wall of the vessel into the extravascular space. A similar histologic appearance can be seen in an available Aperio virtual slide. Just focus on any artery, and you will be able to see margination and extravasation.

Question 52

Which of the following processes are common to immature B cells and double positive thymocytes? * Encounter with antigen can lead to lymphocyte maturation. * Encounter with antigen induces BCR and TCR class-switching. * Encounter with antigen leads to anergy. * IL-2 expression promotes proliferation. * TdT expression introduces random nucleotides into the μ and TCRβ genomic loci

Answer 52

**Encounter with antigen can lead to lymphocyte maturation** - When immature B cells and double positive thymocytes are stimulated by antigen, they can either undergo positive or negative selection. Positive selection results in lymphocyte maturation.

Question 53

The image below depicts a portion of the Peyer’s Patches of the small intestine. Match the following functions with the letters that appear in the photomicrograph. Note that for clarity, some duplicate structures are labeled with the same letters. The site of proliferation and maturation of B lymphocytes is:

Answer 53

B - these are germinal centers

Question 54

Which one of the following signaling intermediates is a kinase that phosphorylates the ITAMS of CD3 peptides when CD4 T cells are activated through their TCR? Lck Jak Calcineurin MyD88 PLCγ

Answer 54

Lck - Lck is a membrane-bound kinase associated with the CD4 coreceptor that augments TCR signaling in T cells.

Question 55

ANA test does what?

Answer 55

E. The antinuclear antibody test measures circulating autoantibodies specific for any of a number of nuclear antigens.

Question 56

A fluorescenated antibody to CD3 was used to stain sections of the spleen of normal mice. Which one of the following is a splenic structure that would be most intensely stained by this antibody? Periarteriolar lymphoid sheath Germinal center Efferent lymphatic Red pulp White pulp follicles

Answer 56

Periarteriolar lymphoid sheath - T cells in the splenic white pulp are most concentrated within the PALS.

Question 57

Superantigens bind?

Answer 57

MHC class II and the TCR

Question 58

What chain is invariant in MHC class I?

Answer 58

Beta chain

Question 59

In which one of the following protein domains are the polymorphic amino acid residues of HLA molecules primarily located? Class I α1 domain Class I α3 domain Class II β2 domain Class II β3 domain β2-microglobulin domain

Answer 59

Class I α1 domain - Polymorphism of both Class I and Class II molecules is located primarily in the membrane-distal domains, such as α1.

Question 60

You are characterizing the macrophage response to the bacterium Pseudomonas aeruoginosa. Knowing that this gram-negative bacterium has a potent endotoxin, you decide to determine if IL-1 transcription is activated in macrophages by the pathogen through a Toll-like receptor. Which of the following signaling intermediates is involved in this pathway? c-Jun NF-kB PLCγ Stat-1 ZAP-70

Answer 60

NF-kB

Question 61

Factor I is responsible for inhibiting which of the following events: C3b cleavage C3a-mediated opsonization C3d-mediated B cell co-activation C4a-mediated opsonization C5 cleavage

Answer 61

C5 cleavage

Question 62

Complement fixation test measures?

Answer 62

complement consumption by antigen-antibody complexes and can be used to measure the amount of antigen or antibody in an unknown sample.

Question 63

LFA-1 binds?

Answer 63

ICAM-1

Question 64

Which one of the following cells of the innate immune system is capable of both high level phagocytosis and high level oxidant production? Dendritic cells Epithelial cells Neutrophils NK cells NKT cells

Answer 64

Neutrophils

Question 65

A clone of antigen-specific mouse B lymphocyes is activated with a protein antigen in vitro in the presence of T helper cells, and the expression of surface Ig molecules on the B cells is followed over time. Which one of the following events is most likely to occur in the B cells? They will change from the expression of membrane IgG to membrane IgD. They will change from the expression of membrane IgG to membrane IgM. They will change from the expression of membrane IgA to membrane IgG. They will change from the expression of membrane IgD and IgM to membrane IgG. They will change from the expression of membrane IgM to membrane IgG and then back to membrane IgM.

Answer 65

They will change from the expression of membrane IgD and IgM to membrane IgG. - When B cells switch isotypes, they first switch from coexpression of IgM and IgD to some other isotype, most often IgG, depending on the signals they receive.

Question 66

Which one of the following cell surface receptors is a member of the CD18 integrin family? ICAM-1 IL-2R Poly Ig receptor TLR2 CR3

Answer 66

CR3 - Complement receptor 3 is a member of the b2 integrin family. It is comprised of a common β chain (CD18) paired with a unique α chain (CD11b).

Question 67

Does the oral vaccine promote a carrier or non-carrier state?

Answer 67

Non-carrier

Question 68

Which one of the following is a component of the innate immune system that can activate complement in a C2-dependent fashion? α-defensin Mannose-binding protein IgG antibody Fibrinogen C-reactive protein

Answer 68

MBP (or **mannose-binding lectin, MBL** m) is a C1q-like protein that binds to microbial mannose residues and recruits MBL-associated serine protease (MASP). This protease has the same specificity as C1qr2s2 and cleaves C4 and C2 of the complement system. This is the lectin pathway of complement activation.

Question 69

Superantigens are toxins produced by the bacteria Staphylococcus aureus and Streptococcus pyogenes. Which of the following explains the ability of these superantigens to induce excessive cytokine responses? ## Footnote Activation by antigen of multiple IgGs, which then activate exponential numbers of allergy-inducing cells, such as eosinophils and basophils Activation of T cells by binding both the TCR and the MHC class II Activation of Toll-like receptors on neutrophils Crosslinking of the BCR by the Fc portion of IgG molecules Crosslinking of the BCR by MHC class I

Answer 69

Activation of T cells by binding both the TCR and the MHC class II

Question 70

Does the intramuscular vaccine promote a carrier or non-carrier state?

Answer 70

Carrier

Question 71

Beta-2 microglobulin is a component of what pathway?

Answer 71

MHC class I pathway

Question 72

In the accompanying low power photomicrograph of lung, the interlobar fissue labeled”F” conveniently divides the picture into halves. The alveoli (labeled “A”) on the left hand side of the picture are most likely filled with which one of the following? ## Footnote Atmospheric dust and debris Collagen Edema fluid Neutrophils and fibrin Macrophages

Answer 72

Neutrophils and fibrin - The alveoli on the right are relatively empty, but on the left they exhibit acute pneumonia, and are filled with neutrophils and a variable amount of fibrin. This is the typical picture of acute inflammation, often due to pyogenic bacteria. The fibrin and neutrophils affect gas exchange, and the patient may become hypoxic. If the inflammation does not resolve quickly (because of antibiotics), the infiltrate may organize, and fibroblasts will lay down collagen and cause long-term scarring of the lung.

Question 73

Which of the following functions is MOST commonly associated with IL-3? Mast cell growth CTL Production Plasma cell differentiation Th2 differentiation Vascular permeability

Answer 73

Mast cell growth - IL-3 induces the growth of mast cells, granulocytes, erythroid cells, and megakaryocytes.

Question 74

A patient with a gram-negative urinary tract infection suddenly becomes septic and you are considering potential soluble mediators of his acute systemic inflammatory response to infection. Which of the following soluble pattern recognition molecules is present in the serum of healthy individuals and would likely have contributed to the pathogenesis of sepsis in this patient? ## Footnote Mannose-binding lectin IgG antibody Interleukin-2 Jak2 kinase T cell antigen receptors

Answer 74

**Mannose binding** **lectin** - Complement has several components that are soluble pattern recognition molecules, including mannose-binding protein (recognizes bacterial mannose). MBP (MBL) is present in serum at high concentrations.

Question 75

What is the letter A in this picture?

Answer 75

M cells

Question 76

The healing soft tissue shown in the accompanying photomicrograph contains pink or hyalinized material interspersed between cell nuclei. Which one of the following words or phrases best describes the composition of this pink tissue? 1. Collagen 2. Edema 3. Fibrin 4. Necrotic tissue 5. Protein

Answer 76

Collagen - The nuclei labeled “F” in the photomicrograph are fibroblast nuclei. Fibroblasts produce collagen, which is secreted, then assembled outside the cell. While collagen is certainly a protein, it is a more specific term, and is thus preferred. Collagen should always be associated with fibroblasts.

Question 77

Which of the following proteins expressed by CD4+ T cells MOST contributes to macrophage activation? CD28 CD154 CD132 IL-4 LFA-1

Answer 77

CD154 - Aka CD40 has two major functions activating macrophages and inducing class switching in B cells

Question 78

Intramuscular vaccines produce what class of antibody?

Answer 78

IgG

Question 79

The Haemophillus influenzae type B conjugate vaccine differs from the older Haemophillus polysaccharide vaccine in that the conjugate vaccine: activates polysaccharide-specific T cell immunity. stimulates formation of protective IgE antibodies. induces memory B cells that produce IgG antibodies. activates macrophages to produce IL-1b. contains an adjuvant.

Answer 79

induces memory B cells that produce IgG antibodies. - Conjugate vaccines are composed of antigens covalently linked to protein immunogens. As such, they stimulate both B and T helper cells. With T cell help, isotype switching to IgG and memory B cell induction can occur. These vaccines are not designed to induce IgE antibodies.

Question 80

Some patients with autoimmune diseases show poor clearance of soluble immune complexes from their blood circulation. This would suggest a defect in the functioning of which one of the following receptors? CR1 CR2 CR3 CR4 FcgR

Answer 80

CR1 - Soluble immune complexes in circulation consist primarily of antigen complexed with either IgM or IgG antibodies. Being complement-activating, these complexes also have associated with them complement fragments derived from the classical pathway of activation. C3b or iC3b are the primary mediators of immune complex clearance from the circulation and bind to CR1 receptors found on erythrocytes.

Question 81

What is C5b6789?

Answer 81

This is the membrane attack complex

Question 82

What is the first step of the complement signaling cascade that is common to the classical, alternate, and lectin pathways? C2 cleavage C3 cleavage C4 cleavage C5 cleavage Factor B cleavage

Answer 82

C3 cleavage

Question 83

CD28 binds?

Answer 83

B7

Question 84

Which of the following is an excellent “costimulator” of B lymphocytes that delivers a second signal to the cells? Antimicrobial peptides C3d Interferon-gamma Interleukin-15 Fc portion of IgG

Answer 84

C3d

Question 85

A 14-year-old boy suffered from a splinter in his right finger, which became infected and inflamed. A large lymph node was found near his elbow, which his mother insisted must be removed. A representative section from the enlarged lymph node is shown at right in the accompanying photomicrograph, along with a normal lymph node that was removed at the same time. Which one of the following is the best diagnosis for the abnormal lymph node? * Diffuse large B cell lymphoma * Follicular hyperplasia * Follicular lymphoma * Hodgkin’s lymphoma * Metastatic carcinoma

Answer 85

**Follicular hyperplasia** - The history suggests a benign, inflammatory process, which is confirmed by the histological appearance. The follicles f. encroach on the medulla, but do not move outside the capsule (as is often the case in follicular lymphoma).

Question 86

Viral antigens can be presented by MHC class I expressed by infected epithelial cells. Which of the following proteins is MOST DIRECTLYresponsible for the destruction of the virus-infected epithelial cells by cells of the adaptive immune system? ## Footnote C5b6789 IFNγ IgA IL-8 Granzyme B

Answer 86

Granzyme B - CD8+ T cells destroy infected cells using either Granzyme B or Fas.

Question 87

Which of the following best describes the function of the CD4 molecule? ## Footnote Binds B7 molecules Binds ICAM-1 Binds non-polymorphine residues of MHC class II Binds superantigens Binds VCAM-1

Answer 87

Binds non-polymorphine residues of MHC class II

Question 88

If the broad bands of collagen seen in the lower half of this photomicrograph were analyzed biochemically, they would be found to contain which one of the following collagen types?

Answer 88

Type 3 - This is a keloid, and type 3 collagen is never remodeled to type 1.

Question 89

Which one of the following proteins or group of proteins can act as an opsonin? C3b IL-8 ß-defensins lysozyme secretory component

Answer 89

**C3b** is an effective opsonin and binds antigen-antibody complexes or C3b-coated microbes to phagocytic cells through their complement receptors (CR3 and CR4).

Question 90

Which one of the following is a property of NKT cells, but not conventional αß T cells? The expression of Rag-1 and Rag-2 Specificity for glycolipid antigens The expression of the co-receptor CD28 Lysis of target cells through a Fas-dependent mechanism Production of IFN-γ

Answer 90

Specificity for glycolipid antigens - While conventional T cells recognize peptide antigens presented by the host MHC molecules, NKT cells recognize glycolipids presented by CD1 molecules on antigen-presenting cells.

Question 91

Which one of the following lymphocyte subsets bears an antigen receptor that recognizes glycolipid, rather than protein, antigens? NKT cell CD8 TCRαβ T cell CD4 CD8 thymocyte Double negative thymocyte Pre-TCR thymocyte

Answer 91

While the TCR of **NKT cells** is comprised of αβ heterodimers similar to those of the conventional TCRs, they recognize glycolipid antigens presented by CD1 molecules.

Question 92

IL-2 does what?

Answer 92

It mediates the activation of cell proliferation in T and B lymphocytes, two component of the adaptive immune system.

Question 93

From analysis of the accompanying high power photograph, how would you classify the acute inflammatory exudates seen? ## Footnote Eosinophilic Fibrinous Fibrous Granulomatous Purulent

Answer 93

Fibrinous - The photomicrograph shows an abundance of fibrin strands f.. By definition, this is a fibrinous exudate. An acute inflammatory exudate on a serosal surface usually contains plentiful fibrin, e.g., as in so-called “bread and butter” pericarditis

Question 94

Which of the following cells is MOST likely to present antigen to CD4+ Th1 cells? B cells Dendritic cells Macrophages Monocytes Neutrophils

Answer 94

Th1 cells are effector cells that migrate to the site of infection. At the site of infection, the most likely APCs found are **macrophages**. DCs migrate to the lymphoid tissues. B cell-T cell interactions are most likely found in lymphoid tissues. Monocytes are in blood. Neutrophils do not express MHC class II.

Question 95

CR2 has what role?

Answer 95

coreceptor found on B cells that coactivates B cells when they bind both antigen (the ligand for the BCR) and the complement peptide C3d (the ligand for CR2).

Question 96

Which one of the following is true regarding the T cell antigen receptor? Its V region genes undergo a high rate of mutation following cell activation by antigen. The cytoplasmic domains of the α and β chains contain several ITAM motifs. It shows a high affinity (Ka \< 100 nM) for peptide-MHC complexes. It signals gene transcription primarily through the JAK/STAT pathway. The receptor is never expressed in the absence of CD3 peptides.

Answer 96

The receptor is never expressed in the absence of CD3 peptides. - TCR are never expressed in the absence of their CD3 peptide partners. This is emphasized by examining CD3-null strains of mutant mice.

Question 97

A patient appears to have an antibody deficiency due to an absence of B cells, and you decide to treat her with IVIG. Fifteen minutes after injecting the drug, you measure her serum IgG level and it is found to be 30 mg/dL. What concentration of IgG would you expect to find in this patient’s serum 6 weeks after drug delivery? Undetectable 3 mg/dL 7 mg/dL 15 mg/dL 30 mg/dL

Answer 97

7 mg/dL - the half life of IgG is approx 3 weeks

Question 98

Administering only the oral polio vaccine has which of the following advantages over administering only the intramuscular polio vaccine? 1. Induces IgA production 2. Induces IgG production 3. Induces a T-dependent antibody response 4. Permits a carrier state 5. Prevents CNS infection

Answer 98

An oral vaccine promotes immunity in which IgA antibody is the dominant type

Question 99

A pediatric patient presents with recurrent infections and you hypothesize that she has a defect in killing phagocytized bacteria. Which one of the assays listed below would best allow you to test this hypothesis? Complement fixation test Quantitative test of immunoglobulins Mixed lymphocyte reaction NBT dye reduction test ANA test

Answer 99

NBT dye reduction test - Nitroblue tetrazolium test meadures the production of oxidants that are important mediators of oxidative damage to phagocytized microbes.