Adaptive Immunity

Question 1

Principle defense against extracellular microbes

Answer 1

Humoral Immunity

Question 2

Promotes destruction of intracellular microbes

Answer 2

Cell Mediated immunity

Question 3

IL-7

Answer 3

Principle cytokine that stimulates the proliferation of B and T cell progenitors

Question 4

Clonal selection hypothesis

Answer 4

Antigen receptors are produced by random DNA recombination events that are not dependent on or influenced by the presence of antigens

Question 5

Somatic recombination

Answer 5

• VDJ combination
• Process of DNA recombination by which the functional genes encoding the variable regions of antigen receptors are formed during lymphocyte development
• Occurs only in immature B and T cells

Question 6

Allelic exclusion

Answer 6

• Protein product of one productively recombined antigen receptor locus on one chromosome blocks rearrangement of the corresponding locus on the other chromosome
• Ensures that each lymphocyte will express a single antigen receptor and that all antigen receptors expressed by one clone of lymphs will have identical specificity

Question 7

Which lymphs have allelic exclusion?

Answer 7

B cell light and heavy chains

TCR b chain

Question 8

Self MHC restriction

Answer 8

T cells only recognize antigens displayed by MHC molecules that the T cell encountered during maturation in the thymus (and thus sees self)

Question 9

CD1

Answer 9

• Class I like non classical MHC molecule

- Bind and display lipids (instead of peptides) to certain types of T cells, particularly NKT

Question 10

MHC Class I

Answer 10

• Expressed on most nucleated cells
• Displays peptides to and recognized by CD8+ T cells
• Composed of 3 genes: HLA- A, HLA- B- HLA-C
• Increased expression can be induced by interferon A, B, G and TNF
• Composed of alpha chain (a3 is conserved among all class I MHC) with beta 2 microglobulin unit
• Accomodates peptides 8-11 residues long
• A3 binds CD8

Question 11

MHC class II

Answer 11

• Normally expressed only on DCs, B cells, macrophages and a few other types
• 3 genes HLA DP, DQ, and DR
• Interferon gamma is principal cytokine
• Composed of alpha and beta chain
• B2 is invariant and binds CD4

Question 12

Where are the mature T cells?

Answer 12

Thymic medulla

Question 13

Most effective for activating naive T cells

Answer 13

DCs

Question 14

Most effective at activating effector T cells

Answer 14

B cells and macrophages

Question 15

Which uses proteosome and TAP?

Answer 15

MHC CLASS I (cytosolic and nuclear protein antigens)

Question 16

What is the process for peptide MHC class II production?

Answer 16

Protein antigens are captured from the extracellular environment–> internalized into endosomes by specialized APCs–> Degradative enzymes in endosomes and lysosomes generate peptides–> MHC II are synthesized int he ER and transported to same endosomes with the invariant chain–> In the endosomal vesicle, invariant chain is degraded, leaving 24 amino acid remnant called CLIP–> CLIP is removed by HLA-DM–> MHC class II is stabilzed and bound to peptide

Question 17

TCR components

Answer 17

• Variable domain
• Hydrophobic transmembrane region
• Constant domain
• Short cytoplasmic region

Question 18

What area recognizes peptide MHC complexes?

Answer 18

V region, specifically concentrated

Question 19

What do T cells require for transition to effector cells?

Answer 19

• First signal is response by the TCR to MHC and peptide on an APC (foreight signal)
• Second signal is costim ligand induced on APC by microbes (danger signal)

Question 20

CD28

Answer 20

• Recognized and binds B7 proteins on activated APCs

Question 21

CTLA-4

Answer 21

• Inhibitory receptor of the CD28 family

- Also bind B7

Question 22

LFA-1

Answer 22

• Binds ICAM-1 on APCs and endothelium and functions to help cell adhesion

Question 23

CD44

Answer 23

• Binds hyaluronan, involved in leukocyte adhesion to endothelial cells and ECM

Question 24

CD45

Answer 24

• Tyrosine phosphatase that regulates T and B cell activation

Question 25

L-Selectin

Answer 25

- Part of selectin family which mediates low affinity adherence of leukocytes as they roll through venules

Question 26

Naive T cells

Answer 26

CD45 RA

Question 27

Memory T cells

Answer 27

CD45 RO

Question 28

Where is antigen binding?

Answer 28

- Hyper variable region of the VH and VL

Question 29

Where does the antigen recognition take place?

Answer 29

FAB

Question 30

Where does the effector function take place?

Answer 30

Fc region

Question 31

Where are all Ig Heavy chain genes found?

Answer 31

Chromosome 14

Question 32

What is the structure of Ig?

Answer 32

Two beta pleated sheets held together by disulfide bridge

Question 33

What differentiaties antibodies into distinct classes?

Answer 33

Structure of their heavy chain C region

Question 34

IgA

Answer 34

- Secreted form is dimer

Question 35

IgD

Answer 35

- Circulates as a monomer | - Naive B cell antigen receptor

Question 36

IgE

Answer 36

- Circulates as a monomer | - Mediates immediate hypersensitivity, defense against helminthes

Question 37

IgG

Answer 37

- Circulates as a monomer - Functions in opsonization, complement activation, antibody dependent cell mediated cytotoxicity, neonatal immunity and passive immunity, feedback inhibition of b cells

Question 38

IgM

Answer 38

- Circulates as pentamer | - Functions in complement activation, naive B cell antigen receptor (monomeric form)

Question 39

B cell maturation steps

Answer 39

- Stem cell - Pro B cell - Pre B cell - Immature B cell (IgM) - Mature B cell ( co -express IgM and IgD)

Question 40

CD19

Answer 40

- Role in B cell activation | - Forms a co receptor complex with CD21 and Cd81 that delivers signals that synergize with signals from b cell antigen

Question 41

CD21

Answer 41

- Receptor for complement fragment C3D - Forms a co receptor complex with CD19 and CD81 that delivers activating signal in B cells, receptor for EBV

Question 42

Phenotype markers of B cells

Answer 42

- MHC class II - CD19 - CD21 - Fc receptors

Question 43

Where does isotype switching happen?

Answer 43

- Germinal center and sometimes extrafollicular foci - Constant regions of the heavy chains change but the specificity of the antibodies (which is determined by the variable regions) remains unaltered

Question 44

Match cytokine to Ig

Answer 44

- IFN gamma--> IgG - IL-4--> IgE - TGF beta--> IgA - B cells in mucosal tissues also switch to IgA

Question 45

Fc gamma receptor 3 (CD16)

Answer 45

- binds IgG - Found on NK cells - Responsible for antibody dependent cell mediated cytotoxicity

Question 46

Fc epsilon

Answer 46

- Binds IgE | - Expressed by mast cells, basophils, and eosinophils

Question 47

Where do T cells reside in the spleen?

Answer 47

Periarteriolar lymphoid sheath

Question 48

Where do B cells reside in the spleen?

Answer 48

- Follicles and germinal centers

Question 49

Genes involved in class switch recombination and somatic hypermutation

Answer 49

activation induced cytosine deaminase Uracil n glycosylase Defects prevent B cells from switching from IGm to IGG.