T and B-Cell Mediated Immunity

Question 1

What happens when MHC/peptide complex first bind to TCR

Answer 1

CD40L expression is upregulated on T cells (CD40 is constitutively expressed on APCs)
Expression of CD80 is upregulated on APCs (CD28 constitutively expressed on T cells)

Question 2

Explain downstream signaling pathway after CD4/CD8 bind MHC

Answer 2

CD4/CD8 associated Src family kinase Lck is activated and phosphorylates ITAMs of CD3 and lambda chains. ZAP70 associates with ITAMs and is phosphorylated and activates PLCy1 and others

Question 3

What happens to T cells that recognize antigen without binding of co-stimulatory ligands

Answer 3

They become anergic

Question 4

Effect of IL-4 released by T cells

Answer 4

B cell switching to IgE

Question 5

Effect of IL-5 released by T cells

Answer 5

Activation of eosinophils

Question 6

Effect of IL-17 released by T cells

Answer 6

Stimulation of acute inflammation

Question 7

Effect of IL-2 released by T cells

Answer 7

Autocrine signal, binds IL-2R

Promotes T cell proliferation and differentiation

Question 8

CD69

Answer 8

Also known as S1P. Binds S1PR1 and impairs migration out of lymph node so that T cell has ample time to be activated

Question 9

Main cytokines of Th17 cells

Answer 9

IL-17, IL-22, TGF-b

Neutrophil recruitment/activation

Question 10

What cytokines cause proliferation of Th1 cells

Answer 10

IFN-y and IL-12, also involves transcription factor T-bet

Question 11

What cytokines cause proliferation of Th2 cells

Answer 11

IL-4, involves TF GATA-3

They secrete IL-4, 5, 13

Question 12

What cytokines cause proliferation of Th17 cells

Answer 12

IL-1, IL-6, also involves TF RORyt

They secrete IL-17, IL-22

Question 13

What surface markers do NK cells express

Answer 13

CD16 and CD56

Question 14

Effector cells that become memory cells will increase expression of what

Answer 14

Bcl-2 anti-apoptotic protein

Question 15

Treg cells and B7/CD80 interaction

Answer 15

Treg cells constitutively express CTLA-4 which binds to CD80(B7) with higher avidity than CD28 and inhibits co-stimulatory signals

Question 16

What is another inhibitory ligand that T/B cells can express

Answer 16

PD-1 expression is inducible of T/B cells and binds B7 to negatively regulate T cells

Question 17

Memory T cells require what for survival

Answer 17

IL-7 and IL-15

Question 18

Co-receptors for BCR include

Answer 18

CD19, CD81, CR2 (CD21)

Question 19

B-2 cells include

Answer 19

Follicular B cells- these are recirculating B cells

Marginal B cells- reside in the spleen

Question 20

B-1 cells are

Answer 20

Mucosal B cells, limited Ag specificity

Question 21

Downstream signaling pathway of B cells when Ag binds

Answer 21

ITAMs of Iga/Igb co receptors are phosphorylated by Src family. Syk binds ITAM and is phosphorylated and triggers downstream response including TFs:
Myc, NFAT, NF-kB, AP-1

Question 22

What is the second part of first signal that completes BCR cross-linking

Answer 22

Ag must also bind CR2 (through C3d which is bound to microbial Ag) and receive costimulatory signal through CR2 & CD19, as well as Iga/Igb
Or TLR can be activated alongside BCR through PAMP recognition

Question 23

Change in CXCR5 and CCR7 expression in newly activated T cells vs B cells

Answer 23

Newly activated T cells will increase CXCR5 expression and decrease CCR7 expression
Newly activated B cells will increase CCR7 expression

Question 24

Do class switching and affinity maturation occur at the same time

Answer 24

Usually

Question 25

AID

Answer 25

CD40/CD40L interactions and cytokines increase expression of AID in B cells. AID introduces point mutations by switching Cs to Us, allowing Ape I endonuclease to create ds breaks in DNA, generating high affinity antigen-specific Abs.

Question 26

T follicular helper cells

Answer 26

Express CD4, low levels of CD25, ICOS (essential for germinal center reaction) Secrete IL-21 - facilitates differentiation to plasmablasts Secrete IFN-y and IL-4 for cytokine switching

Question 27

Plasma cells

Answer 27

Decreased CD19, CD20, MHC II expression Increased CD27 expression Secretory Ig only Expanded ER

Question 28

B1 B cells and marginal zone B cells respond to

Answer 28

T-independent responses (non-protein Ags) | Secrete mostly IgM, short lived plasma cells

Question 29

Follicular B cells respond to

Answer 29

T-dependent responses | Isotype switching, high affinity Abs, long lived plasma cells

Question 30

Which Ab is capable of blocking its own production and how does this happen

Answer 30

IgG only | FcyRIIb receptor associated SHIP protein- converts PIP3 to PIP2, blocking downstream signaling

Question 31

Effector functions of Abs are mediated by which region of Ig

Answer 31

Fc region (effector functions are mediated through Fc region, but all functions are triggered by binding of Ag to the Fab region

Question 32

FCyRIIIA receptor

Answer 32

Expressed by NK cells, permits antibody dependent cellular cytotoxicity

Question 33

How is IgG able to cross into fetal circulation

Answer 33

It leaves circulation via transcytosis via FcRn, which transports IgG across the placental barrier FcRn is expressed on endothelial cells, macrophages and other cell types

Question 34

Active vs passive immunization

Answer 34

Active is the introduction of an antigen that provokes and adaptive immune response Passive is the introduction of an antibody/antiserum into a naïve recipient