Immunology Midterm #2

Question 1

What is humoral immunity?

Answer 1

B cell immune factors which are dissolved in the extracellular fluids (complements and antibodies)

Question 2

What is clonal selection?

Answer 2

Rapid reproduction of a single clone (single b cell with a specific epitope)

Question 3

What is an antibody?

Answer 3

are B cell receptors (BCRs) which are secreted in the blood. aka immmunoglobulins

Question 4

What is affinity? How does it relate to the antigen binding sites?

Answer 4

Affinity is the strength which as antibody or other receptor binds to an epitope. Certain antigens bind better to some sites than other. However, an imperfect fit can still cause a reaction and cause Abs to be released

Question 5

What determines the shape of the antigen binding site?

Answer 5

VDJ recombination

Question 6

What are the differences between V and C segments?

Answer 6

V - variable segment - determines which antigen binds to the epitope site as a result of VDJ recombination

C - constant segment - defines the function of the antibody

Question 7

When is a receptor not an immunoglobulin?

Answer 7

When it doesn’t activate the immune system ie blood glucose receptors

Question 8

Is a T cell receptor an immunogloblulin? an antibody?

Answer 8

Immunoglobluin: yes

Antibody - no

Question 9

What enzymes can split an antibody? What are the functions of the Fab and Fc?

Answer 9

Split by proteases such as papain protease

Fab (Fragment of antigen binding) - antigen binding, neutralization, agglutination

Fc (constant fragment) - opsonization, complement receptor binding

Question 10

What are the events of Ab production and specification?

Answer 10

1. VJD recombination produces a IgM antibody with a specific antigen binding site
2. The B cell is exposed to an antigen
3. The C section undergoes recombination, depending on what is required
4. Clonal selection expands required population

Question 11

What is class switching?

Answer 11

Changing the function of an antibody by switching the Fc.

Done by a process of looping and cutting until the correct Ab is at the front

Question 12

What is IgM? What is the shape? Function? Special Characteristics?

Answer 12

Immunoglobulin prior to C recombination.

As a monomer - interacts with APCs or pathogens

As a pentadimer - secreted in blood. Compliment fixation and agglutination

Question 13

Provide a summary of the different antibodies and the # of binding sites,

if it crosses the placenta

fixes complements

binds to what cells

function

Answer 13

Question 14

How does IgD compare to IgM?

Answer 14

Thought to have similar functions to IgM - agglutination and compliment fixation

Question 15

What is IgA? What is the shape? Function? Special Characteristics? How many classes?

Answer 15

Antibody found in secretions

Antibody found in seromucous secretions (saliva, breastmilk, colostrum, genitourinary). Coated with glycoprotein which protects mucous membrane from antigen attachment

Travels through the epithelium - gains epethilial receptor to stabilize IgA

Shape - dimer

Classes: 2

Question 16

What is IgG? What is the shape? Function? Special Characteristics? Classes?

Answer 16

80% of circulating antibodies. Monomers. Long lived. 4 classes

Function: Neutralization, opsonization, compliment fixation. Not as great with agglutination

Features: Can cross placenta to give fetus passive immunity, Has memory

Question 17

What is IgE? What is the shape? Function? Special Characteristics?

Answer 17

Scarce Ig. Only elevated in certain conditions (parasitic infections and allergies). Attaches to eosinophils and basophils

Question 18

How do antibodies promote pathogen killing?

Answer 18

ANtibodies will attach to specific cellular receptors which dictates what will happen

ie IgG will bind to a Fcy receptor and cause opsonization

Question 19

What are the effects of antibodies of agglutination? What is a clinical practice based on this?

Answer 19

Antibodies with multiple Fab sites clump antigens together to make for easy digestion (ie kitty litter) (IgM has 10 Fab)

Blood typing: antibodies for a certain blood type are placed in a blood sample. If the antibodies match the blood type, the sample with be clear with visible clumps

Can also clump precipitates from a solution,

Question 20

What are the effects of antibodies of neutralization? Clinical relevance?

Answer 20

ANtibodies block the attachment of microorganisms to susceptible tissues and cells (ie IgA)

HIVmab B12 blocked the HIV virus from entering CD4 cells. Prevent exotoxins from entering cell by preventing binding (antitoxins)

Question 21

What are the effects of antibodies on oponization?

Answer 21

ABs can activate the compliment system, or can improve phagocytic abilities of cells (macrophages) by coating the macrophage with Abs (IgG)

Question 22

What is antibody dependent cell mediated cytotoxicity? Examples?

Answer 22

Part of the normal immune response but can cause damage to tissues when prolonged.

Ie - opsonization - binds to the Fc of pahgocytes

Frustrated phagocytosis - target is too large to engulf, so digestive enzymes are secreted which can cause inflammation of normal tissues

Eosinophil response - IgE bound cells secrete toxins and toxic factors

Question 23

What are the effects of Ab on complement activation?

Answer 23

Ab-Ag complexes activates the complement factors by the classical pathway which results in chemotaxis, inflammation, opsonization and the formation of MAC

The antibodies themselves do not induce chemotaxis, but the complement factors (C3a, C5a)

Question 24

What do Tc cells use to MHCI? What protein binds to MHC2

Answer 24

Tc use CD8 to bind to MH!

CD4 binds to MH2

Question 25

What cells bind to MHC2?

Answer 25

APCs, Th cells, B cells

Question 26

What are the effects of interleukins on the humoral response?

Answer 26

An antigen interacts with an APC. IL2 stimulated Th0 (naive Th cells) which can result in Th1 stimulation (Tc cell reproduction) or Th2(humoral response). Th2 is stimulated by IL4 which produce memory cells and B plasma cells (makes antibodies)

Question 27

What are the effects of ILs on class switching?

Answer 27

T helper cells secrete interleukins which can stimulate the Fc DNA recombination (FC = functional part of Ab) Can also stimulate the proliferation of the specific classess (IgA, D,E,G,M)

Question 28

What is the process of formation of memory and plasma B cells?

Answer 28

1. Clonal Selection & Antigen binding - B cell recognizes microbes and their antigens, and binds to the microbes with the B cells Ig receptors. This is the initial selection of the proper VJD clone reproduction. 2. Antigen Processing and Presentation - Once the microbe is attached, it is endocytized to the B cell. The B cell breaks it into small proteins and displays them on the MHC 2 complex. This readies the antigen to be presented to a T helper cell 3. B Cell/Th Cell Cooperation and Recognition - The T cell was activated by a APC. The B cell and Th cell link - B cell MHC2 joins with Th antigen receptor and CD4 4. B cell activated- T cell gives off additional signals (interleukins) and B growth cell factors. The linked receptors and chemical stimuli activates the B cell causing an increase in cell metabolism causing cell enlargement, proliferation and differentiation 5. Clonal expansion / memory cells - Activated B cell undergoes mitotic division creating clones with receptors specific to the antigen. Memory and plasma cells are produced. Memory cells are persistent, long term cells which will react with the antigen on future exposures 6. Plasma cells/ antibody synthesis - Plasma cells are short lived, ctive secretory cells which synthesize and release Abs. Abs have the same specificity as the Ig receptor and circulate in the plsama where they will react with the antigens and microbes

Question 29

Where does VJD recombination take place in the body? Class switching? Maturation?

Answer 29

VJD: Bone marrow Class & maturation - secondary lymphoid organs

Question 30

Can B cells intiate a humoral response without Th cells?

Answer 30

B cells come in direct contact with the antigen. They can mount a small & slow response - less sensitive However, they are activated much quicker with Th cells present

Question 31

Compare B effector and memory cells

Question 32

What is the difference between primary and secondary response?

Answer 32

Primary: response of the B cells after the first encounter with the antigen. Slower, IgM predominantly Secondary: generated after the B cells are exposed to the antigen a second time. Faster and stronger response

Question 33

What are the four stages of immune response?

Answer 33

1. Latent/ Lag - Infection has occured and antigen is present; no Ab in body 2. Log - Rapid (exponential increase of Ab production) 3. Plateau - Ab titer reaches maximum and stabilizes 4. Decline Phase - Ab levels reduce to lower levels

Question 34

Why do we give vaccinations?

Answer 34

1. Shorter exponential growth period in exponential phase in second exposure 2. Second exposure - more IgG than IgM (IgG is stronger) 3. Plateau remains longer in second exposure 4. Slower decline phase

Question 35

What are the differences between primary and secondary exposure?

Answer 35

Primaryo: no px exposure to Ag therefore no memory cells. Longer lag period, shorter plateau and decline. Slowwer rate of Ab productoin, makes less for entire exposure. Abs have a lower affinity to Ag. Primarily IgM. Secondary: Previous exposure, memory cells. Shorter lag period, Longer decline and plateau. Increase rate of Ab prodcution. IgM may or may not be first released. IgG dominated

Question 36

What is serology?

Answer 36

Traditional test for Abs, Ag and cytokines in serum, urine CSF, saliva and tissues

Question 37

What are agglutination and precipitation tests? What are examples?

Answer 37

Antibodies cause microbes with antigens to clump together and fall out of the solution. (Agglutination = cells clumping; Precipitation = proteins). Tubes of antigens are set up, and the serum is diluted you can measure the amount of antibody in the serum. Amount of Ab = titre ie = Widal test to test for typhoon fever. S typhi are cultured and a known amount of antigen is added. Pt serum is mixed with antigen. If titer is 1/40, test is negative

Question 38

Are the cell mediated at humoral immune systems reduntant?

Answer 38

No. There is some overlap (both targen antigens and have memory) However, T cells are better with intracellular pathogens. B cells are better with extracellular pathogens

Question 39

What is DiGeorge Syndrome?

Answer 39

Ppl born without a thymus. Can cope with extracellular pathogens, but cannot effectively combat inctracellular pathogens

Question 40

How does MHC I function?

Answer 40

Old proteins are digested in a proteosome. Fragments are excreted and bound to MHC I. If protein fragments are recognized as foreign, Tc attack

Question 41

How is it determined if Th0 will change into Th1 or Th2

Answer 41

Cytokines such as IL2,4 or TNF and IFN gamma

Question 42

What is the process of Th0 cells differentiation?

Answer 42

Naive Th0 are exposed to an antigen. Random selection if cells become Th1 and Th2

Question 43

What to Th1 and Th2 cells secrete? What are the effects on the immune system?

Answer 43

Th1 secretes TNF & IFN gamma to stimulate a cell mediated response (macrophages, dendritic cells) Th1 cells also secrete IL2 which stimulates Tc cells ( cell mediated response) Th2 cells secrete IL4 which stimulated B cells (humoral response)

Question 44

What is electrophoresis? How does it work? Clinical applications?

Answer 44

Separation of proteins by size by applying an electrical field over a matrix (ie motorcycles can move faster through traffic compared to cars). Helps with identifying exotoxins Can help identify the stage of advancement of HIV. As bands get darker as infection progresses (gp 120 & p24 are important for HIV)

Question 45

What are the differences between monocolonal vs polyclonal Ab production for medical diagnosis? When would each be used?

Answer 45

Monoclonal - Spleen B cells of mice are fused with myeloma cancer cells (hybridoma cells). Much longer lasting than plasma cells. Researchers can select on single epitope and make millions of copies. More specific than polyclonal, but has weaker response. Used for testing for specific diseases such as HIV Poly Clonal - antigen is injected into an animal. Blood is collected, serum isolated and purified with IgG. All the epitopes are collected. Cheap. More sensitive (illicits stronge response) but is less specific. Risk of cross reactivity. Confirms that something is there

Question 46

How is conjugation used for diagnostic tests? What are some clinical implications?

Answer 46

Fc can be attached to a marker (dye, magnet). The Fab will attatch to the antigen being searched for ie Her2/neu is highly expressed in some breast cancers. A flourescent molecule is attached to an Ab that targets Her2/neu. Anti her2 Ab conjugate together, can flouresce under microscope

Question 47

What is flow cytometry? How is it applicable clinically?

Answer 47

Cells are labelled by flouresecent staining. FACs measures the brightness of each cell (how much antigen is in each cell). Can separate stained vs unstained cells ie how many CD4+ cells in microliter of blood. antigen/ cell or # of +ve antigen cells

Question 48

What is ELISA? Clinical applications?

Answer 48

Enzyme linked immunosorbent assay. Measures the amount of Ab in a protein sample. ie Allergy tests. Coat a well with the antigen (allergen). Add pt serum with AgE. If pt is allergic, IgE binds to allergen. Elisa counts congugated dte/isotope

Question 49

What is immunoblotting?

Answer 49

Combination of electrophoresis and immunostaining (markers with Abs). Proteins are separated by size and the specific antigen is detected by immunostaining

Question 50

What is cell mediated immunity?

Answer 50

Responses from the adaptive immune system (T cells) and innate immune system (macrophages & dendritic cells) work together to overcome infection

Question 51

What is mycobacterium TB? Why is the adaptive immune system important?

Answer 51

TB is phagocytized by macrophages in the alveoli. TB prevents the fusion of the lysozone with granulosomes. TB will continue to divide until it is exocytized (it is not destroyed). Abs are ineffective because the diseases is intracellular. instead, macrophages and t cells surround parasitized cell (attracted by cytokines) and results in a TB jail called granuloma

Question 52

How do T cells mature?

Answer 52

in the thymus, hematopoetic cells influence under the influence of thymic peptide hormones (Thymuln, Thymosin, thymopoieten)

Question 53

What are thymocytes? What is the maturation process of a thymocyte

Answer 53

Thymocyte - immature T cells. Can evolve to Th or Tc Step 1 - Immature thymocytes undergo positive selection. Have two periods. Selection of useful thymoytes (have T cell receptors). Cytokine and chemical communication dictates if cells are to be Tc (CD3+,4-, 8+) or Th (CD3+, 4+, 8-) 1. Double negative. Occurs in subcapsular region (CD-3,-4,-8) 2. Double positive. Thymic cortex (CD +3+4+8). Dendritic cells reject cells which lack proper receptors Step 2 - Clonal deletion. Autoreactive T cells are identified and destroyed by dendritic cells and nurse cells

Question 54

What is positive selection?

Answer 54

1. Double negative thymocytes lack T cell receptors (3,4,8) 2, Double positive thymocytes have all the receptors (3.4.8) 3. Cortical endothelial cells mediate positive selection. Uses MHC 1&2 4. dendritic cells mediate negative selection 5. Cytokines and chemical communications determine if cells mature into CD4 (Th) or CD8 cells (Tc)

Question 55

How are T cell surface proteins associated with leukemia?

Answer 55

Surface proteins change during development. Not just CD3,4 and 8. This rapidly expanding population may result in cancer. They may stil retain the cell surface markers of the original cell type

Question 56

What is CD34 most important for?

Answer 56

Important for heatopoetic stem cell selection

Question 57

What is erythrocyte rosetting? What is its clinical application?

Answer 57

CD2 can bind to RBCs of other species. Using this process, T cells can be isolated from blood. 1. sRBCs are added to a blood sample 2. CD2 cells aggregate to sRBCs, resulting in clumping 3. Blood is centrifuged through an oily mixture 4. T cells and sRBCs collect at the bottom. B cells and macrophages at top

Question 58

How does StemSep separate T cells??

Answer 58

APplies a magnetic force to T cells and separates them based off of their receptors 1. Obtain blood sample. Sort for cells that are CD8+ 2. Sort these blood cells for CD4+. Discard cells which care CD4+

Question 59

How is CD3 involved with TCR?

Answer 59

Involved with cellular interactions. **Integrins** are involved with cellular adhesion. Similar to iCams. Allows T cells to stick to other cells Involved with cell regulation 1. Activation - binds antigen to receptor 2. Differentiation - dictates whether Th or Tc 3. Proliferation - multiplication

Question 60

What is signal transduction? What does it do?

Answer 60

ST: protein complexes on the inside of the cell which coordinate a cellular response to extracellular signals Extracellular signals may cause ST to * increase intracellular energy state * Change cellular behavoiur (proliferation) * Apoptosis * Gene expression * Cell differentiation

Question 61

What is clonal deletion?

Answer 61

Removal of autoreactive developing T cells by dendritic and nurse cells. 98% of T cells die at this stage

Question 62

What are the differences between Th1 and Th2 with inflammation?

Answer 62

**Th1** is proinflammatory. Responsible for the infiltration of T cells / leukocytes to the site of inflammation. Prolonged inflammation can lead to tissue damage **Th2** is anti-inflammatory in early stage. IgE is the exception (allergy inflammation). Th2 decreases cel emdiated responses Th1 and Th2 are antagonistic to each other

Question 63

How do Th1 and Th2 work during pregnancy?

Answer 63

Because the father's DNA would mean that the fetus would be recognized as foreign (not self), Tc would attack the fetus. There is a Th2 shift during pregnancy. Anti-inflammatory reaction. Those suffering from inflammatory diseases have a reprieve from pregnancy

Question 64

Do Tc cells phagocytize pathogens?

Answer 64

NO

Question 65

What is an immunological synapse? How strong is it?

Answer 65

Point which Tc cells contact their target (pathogens). It is not very strong. Requires several receptors to increase the strength of the synapse

Question 66

How are immunological synapses strengthened?

Answer 66

1. A large number of TCR/Antigen interactions 2. MHC 1/CD-8 co-receptor interactions 3. Expression of iCAMs on the surface of Tc

Question 67

How to Tc cells cause cell death?

Answer 67

1. Secrete perforins which form aqueous pores- Similar to the complement system. Results in cell lysis and death 2. Granzymes - serin esterases. May trigger cell apoptosis and DNA degredation 3. FAS ligand signalling - Ligand binds to FAS receptor which triggers cell apoptosis

Question 68

Why do Tc cells need to make direct contact with their targets? What would happen if they attacked by proximity?

Answer 68

If the Tc cells released their enzymes by proxy, other close cells could be affected, starting an inflammation cascade. WOuld be be non specific reaction

Question 69

Do T cells have immunological memory?

Answer 69

All T cells have memory. For example, Th cells have Thmemory and TH effector. Tc memory and Tc effectors. In comparison to B cells, T cells respond faster, but the response is shorter and not as effective (don't require class switching and Ab production)

Question 70

How does the TB skin test utilize T cell memory?

Answer 70

1. If a person has been exposed to live TB (disease/ vaccine), they will produce T cells specific to TB 2. Immunological memory is formed 3. TB test injects prified protein derivatives transdermally 4. Deindritic cells process the TB abd display it on MHC II 5. Previously sensitived TH1 cells recognize the pathogen and release cytokines 6. attract macrophages and Tc cells to destroy the disease 7. Produces reaction

Question 71

Will a TB test cause an immunological rxn?

Answer 71

Ideally, the amount of antigen delivered for the TB test is such a small amount that it won't illicit a rxn. However, it depends how sensitive the individial is to antigen- dependant inflam responses

Question 72

What are TILs?

Answer 72

T cells which are found in close association with tumors. Recognize tumor specific antigens. Can be removed for chemo and put back in afterwards

Question 73

How are TILs isolated and cultured? Why?

Answer 73

The tumor is excised and tissue is grown in a petri dish with nutrients and IL2 (IL2 stimulates T cell division. In 1-2 weeks, a carpet of lymphocytes form Retroviruses are used as a vector, which have been genetically spliced to produced TNF (causes apoptosis of cancer cells). Virus infects TILs = TILs which overexpress TNF

Question 74

What are the difference between CD4 and CD8 receptors?

Answer 74

CD4 = T helper CD8 - Tc

Question 75

How long does it take for HIV to infect CD4 cells

Answer 75

about 1 day

Question 76

What happens when T helper cells are attacked by HIV?

Answer 76

If Thelper cells die, can't stimulate the innate immune system (macrophages/ dendritic cells), some Tc cells, and the humoral immune system (antibodies) with cytokines. The body loses the ability to use MHC II to differentiate foreign pathogens

Question 77

How effective are HIV vaccines that illicit am Ab response? Is the MHCI response sufficient to prevent AIDs? Is it effective?

Answer 77

1. Abs aren't verry effective? 2. Not sufficient - pharmatherapeutics can help decrease the viral load to give body a chance to fight the virus 3. Some what effective

Question 78

Why can Tc cells attack HIV when HIV disables Th cells? What mechanism does HIV have against these attacks?

Answer 78

Proteins produced within the cell are degrade by proteosomes when they are no longer useful. These fragmens enter the secretory pathway of the cell and bound to MHC I. Tc cells will directly attack non self antigens (Th cells not involved). Tc cells can recognize and lyse HIV infected cells HIV can fight back by releaseing HIV nef protein (reduces the cellular expression of MHC I causing Tc to be unable to recognize HIV antigens)

Question 79

How do vaccines based on retrovirus envelope work? Are they effective in progressed disease? Example

Answer 79

Vaccines which produce neutralizing Abs. Rarely induce CD8 response. Not effective in stopping diasease because virus is killing Th cells. ie B12 Monoclonal Ab

Question 80

How could the Canarypox virus (CPV) be used against HIV? What vaccines have been based off of this theory?

Answer 80

CPV is not pathogenic in humans, but stimulates a Tc response. Currently genetically combining HIV proteins in CPV. CPV will attract Tc, HIV antigens activate Tc cells. Has been shown to kill HIV cells in patients. Modified Vaccinia Ankara B - modified small pox vaccine with HIV subtype B proteins expressed. Caused an increase in CD8 lymphocytes

Question 81

What is the benefit of giving a prophylactic HIV vaccine? Example?

Answer 81

Individual creates Abs against HIV (immunologic memory). . If individual is infected, memory should be able to fight off infection. However, not all individuals develop same type of Abs. IgG responses provided the best protection against HIV. IgA provided the worst protection (Possibly because it retained a portion of HIV in the secretory portion) Need to develop a way to stim an IgG response

Question 82

How do Tc cells prevent the reactivation of EBV? What can be done clinically?

Answer 82

Tc patrols and eliminates cells expressing EBV antigen (which supresses the infection). HOwever, if pt becomes immunocompromised (chemo/ transplantation) the disease may be reactivated. Transplant tissue may also infect an seronegative person with EBV. Everyone who receives a transplant has a 50% chance of developing post-transplantation lymphoproliferative disease. HOwever, if Tc cells are transpanted, this reduced the risk of developing PTLD to 25%.

Question 83

WHat is EBV?

Question 84

What is cell mediated immunity?

Answer 84

Responses from the adaptive immune system (T cells) and innate immune system (macrophages & dendritic cells) work together to overcome infection