First Aid: Immunology Flashcards Preview

USMLE Step 1 Prep > First Aid: Immunology > Flashcards

Flashcards in First Aid: Immunology Deck (37):
1

What are the functions of lymph nodes?
What causes lymph nodes to swell?

Nonspecific filtration by macrophages, storage of B and T cells, immune response activation

Paracortex enlarges in extreme cell response e.g. viral infection

2

What are contained within the follicle, medulla and paracortex of lymph nodes?

Follicle - B-cell localization and proliferation
Medulla - Medullary cords w/ closely packed lymphocytes and plasma cells and Medullary sinuses w/ macrophages
Paracortex - T-cells and high endothelial venules through which T/B cells enter blood

3

Where are the following cell types found within the spleen? Macrophages, RBCs, T cells, B cells, antigen presenting cells (APCs)

T cells - periarterial lymphatic sheath of white pulp
B cells - follicles of white pulp (germinal centers)
Macrophages and RBCs - in Red pulp
APCs- Marginal zone between red/white pulp (specialized Bcells also here)

4

What are asplenic patients at risk for (name specifically)?

decreased C3b opsonization by macrophages --> increased susceptibility to encapsulated organisms

SHiNE SKiS: Strep pneumo, H. flu type b, N. meningitidis, E. coli, Salmonella spp., Klebsiella pneumo, Strep-group b

5

What are the components of the thymus and what do they contain? Where do T and B cells mature?

T cells = Thymus
B cells = Bone marrow
both are produced in bone marrow

Cortex is dense with immature T cells and medulla is pale with mature T cells and Hassall corpuscles

6

What are the components of the thymus and what do they contain? Where do T and B cells mature?

T cells = Thymus
B cells = Bone marrow
both are produced in bone marrow

Cortex is dense with immature T cells and medulla is pale with mature T cells and Hassall corpuscles

7

What are key features in pathogen recognition within the innate immunity?

Toll-like receptors (TLRs): recognize pathogen-associated molecular patterns (PAMPs)

e.g. LPS (g- bacteria), flagellin (bacteria, ssRNA (viruses)

8

Where do the various MHC receptors bind, how are they encoded, and which cells express these?

MHC I - encoded by HLA -A,B, & C; binds TCR and CD8; expressed on all nucleated cells (not RBCs)

MHCII - encoded by HLA-DR, DP, DQ; binds TCR and CD4; only on APCs

9

Where do the various MHC receptors bind, how are they encoded, and which cells express these?

MHC I - encoded by HLA -A,B, & C; binds TCR and CD8; expressed on all nucleated cells (not RBCs)

MHCII - encoded by HLA-DR, DP, DQ; binds TCR and CD4; only on APCs

10

Match the HLA subtypes with associated diseases:
A3, B27, DQ2/DQ8, DR2, DR3, DR4, DR5

A3 - hemochromatosis
B27 - PAIR (Psoriatic arthritis, Ankylosing spondyltiis, arthritis of Inflammatory bowel disease, Reactive arthritis)
DQ2/DQ8 - Celiac disease
DR2 - MS, ha fever, SLE, goodpasture syndrome
DR3 - DMT1, SLE, graves disease
DR4 - Rheumatoid arthritis, DMT1
DR5 - Pernicious anemia --> VB12 def., Hashimoto thyroiditis

11

How do Natural killer cells destroy cells and what factors enhance their activity?

Induced to kill when exposed to nonspecific activation signal on target cell and/or absence of MHC I on target cell surface

Use perforin and granzymes to induce apoptosis of virally infected cells and tumor cells.

Also kills via antibody-dependent cell mediated cytotoxicity

Enhanced by IL2, IL12, IFN-beta, IFN-alpha

12

What are two methods by which T-cells can differentiate and where does this occur?

Positive selection (thymic cortex) - T cells expressing TCRs capable of binding surface self MHC molecules survive

Negative selection (medulla) - T cells expressing TCRs with HIGH affinity for self antigens undergo apoptosis

13

What are two methods by which T-cells can differentiate and where does this occur?

Positive selection (thymic cortex) - T cells expressing TCRs capable of binding surface self MHC molecules survive

Negative selection (medulla) - T cells expressing TCRs with HIGH affinity for self antigens undergo apoptosis

14

What are two very important interactions that need to occur to activate a T cell to secrete cytokines?

1. phagocytosed antigen is presented by APC onto MHC class II receptor and recognized by TCR on CD4+

2. B7 on APC binds CD28 on CD4+ T cells activating them

15

How does B-Cell activation and class switching occur?

1. Antigen bound and endocytosed by B-cell (begins secreting IgM)
2. Active B cell presents antigen to CD4+ Th cell and CD40 on Bcell binds CD40 ligand on Tcell
3. Th cell secretes cytokines that determine Ig class switch of B cell

16

What are the differences between Th1 helper cell and Th2 helper cell?

Th1 - secretes IFN-gamma to activate macrophages and IL2 to activate CD8+

Th2 - secretes IL 4, 5, 6, 13 --> recruits eosinophils and promotes IgE production

17

How do cytotoxic T cells function? What protein structure allows this to occur?

Kill virus infected, neoplastic and donor graft cells by inducing apoptosis (perforin and granzyme method)

CD8 binds MHC 1 on virus infected cells

18

A culture of cells are identified with lymphocytic origin. They produce CD3, CD4, CD25 and FOXP3 cell surface markers. What are these cells and their function?

Regulatory T cells - maintain specific immune tolerance by suppressing CD4 and CD8 T cell effector functions.

Produce anti-inflammatory cytokines (IL10 and TGF beta)

aka dampen the immune response

19

A culture of cells are identified with lymphocytic origin. They produce CD3, CD4, CD25 and FOXP3 cell surface markers. What are these cells and their function?

Regulatory T cells - maintain specific immune tolerance by suppressing CD4 and CD8 T cell effector functions.

Produce anti-inflammatory cytokines (IL10 and TGF beta)

aka dampen the immune response

20

What are the unique properties of the Fab and Fc portions of the antibodies?

Fab - light and heavy chain portion + unique antigen binding fragment

Fc - heavy chain portion only
C = Constant, Carboxyl terminal, Complement binding, Carbohydrate side chain, Determines isotype (IgM, IgA etc.)

21

What are three main roles of antibodies?

1. Promote phagocytosis
2. Prevent bacterial adherence
3. Activate complement cascade --> enhance opsonization and lysis

22

What are three main roles of antibodies?

1. Promote phagocytosis
2. Prevent bacterial adherence
3. Activate complement cascade --> enhance opsonization and lysis

23

What are the default immunoglobulins expressed by mature B lymphocytes and what could they become? how does that occur?

IgM and IgD on surface by default

Isotype class switching can occur in germinal center of lymph nodes --> become Plasma cells secreting IgA, IgE, IgG

CD40 ligand and cytokines mediate this switch

24

What is the role of IgG?

Most abundant in SERUM, and main Ab in delayed antigen response; fixes complement; crosses placenta (passive infant immunity); Opsonizes bacteria; neutralizes bacterial toxins and viruses

25

What is the role of IgA?

Prevents attachment of bacteria and viruses to mucous membranes; monomer in serum, dimer when secreted; released in secretions (tears, saliva, mucus, breast milk)

most abundant overall

26

What is the role of IgM?

Immediate response to an antigen. Fixes complement (does not cross placenta). Monomer on B cells, pentamer when secreted

27

What are the roles of IgD and IgE?

IgD - unclear function (on B cells and in serum)

IgE - Binds mast cells and basophils; cross links when exposed to allergen --> immediate type I hypersensitivity rxn via histamine release; immunity to worms via eosinophils. lowest concentration in serum

28

What are the roles of IgD and IgE?

IgD - unclear function (on B cells and in serum)

IgE - Binds mast cells and basophils; cross links when exposed to allergen --> immediate type I hypersensitivity rxn via histamine release; immunity to worms via eosinophils. lowest concentration in serum

29

Why do some vaccines require boosters? (e.g. pneumococcal vaccine)

Thymus independent antigens are produced because they lack a peptide component (e.g. LPS from g- bacteria). Cannot be presented by MHC to T cells so weakly immunogenic.

30

Name the positive (upregulated acute phase reactants):

What cytokines induce their release?

Serum amyloid A, C-reactive protein, Ferritin, Fibrinogen, Hepcidin

Induced by IL6, IL1, TNF alpha, and IFN gamma

31

How is the classic complement pathway mediated? What is the final product of complement cascade?

IgG or IgM
Membrane attack complex (MAC)

32

What disorder may cause complement mediated lysis of RBCs?

GPI anchor deficiency (DAF) --> paroxysmal nocturnal hemoglobinuria

33

What is the purpose of IL 10, IL 12, TNF-alpha and interferon-gamma?

IL 10 - MODULATES inflammatory response (inhibits action of active T cells and Th1)

IL 12 - induce differentiation of T cells into Th1, activate NK cells, B cells may secrete

TNFa- Mediates septic shock, activates endothelium, causes leukocyte recruitment, vascular leak

IFNg - Antiviral and antitumor properties; activates NK cells to kill virus infected cells, increases MHC expression and antigen presentation in all cells

34

What are CD 15, 16 and 19 cell surface markers specific for?

CD15 - granulocytes and Reed Sternberg cells (used to dx Hodgkins dz)

CD16 - low affinity Fc receptor on NK cells, neutrophils and macrophages

CD 19 - B cells

35

Two major cytokines that dampen the inflammatory immune response:

IL 10 and TGF beta

36

Two major cytokines that dampen the inflammatory immune response:

IL 10 and TGF beta

37

Describe the 4 hypersensitivity reactions in simple form:

ACID

I. Anaphylactic and Atopic
II. Cytotoxic (antibody mediated)
III. Immune complex
IV. Delayed (cell mediated)