Exam 2 Lecture 11: Antibody Production

Question 1

Immunoglobulins

Answer 1

B cell expresses only 1 unique immunoglobulin on the cell surface
Many identical molecules of Ig are present
Secretes an almost identical Ig- lacks transmembrane domain

Question 2

What is allelic exclusion

Answer 2

Ensures individual B cell produces only one antibody

Question 3

What are the key components of BCR signaling

Answer 3

-Receptor(s) that binds antigen (BCR)
-complex that facilitates intracellular signaling (Igα, Igβ)
-co receptor (CD19, CD81, CR2)
-intracellular kinases that phosphorylate ITAM domains (Blk, Fyn, Lyn, Syk

Question 4

What types of antigen can the BCR recognize

Answer 4

Proteins: surface bound and soluble

Question 5

In secondary lymphoid organs, what is the function of follicular dendritic cells (FDCs)

Answer 5

Stromal in origin
Take up intact pathogens and antigens to preserve
Use surface receptors to extract whole antigens from the lymph

Question 6

Where do B cells go if they don’t encounter their cognate antigen

Answer 6

Leaves via efferent lymphatics following S1P gradient

Question 7

Where do B cells go after they encounter antigen on FDCs

Answer 7

Upregulates CD69 which blocks S1) signaling and allows B cell to remain in the lymph node and move to border between TCZ and BCZ
Meet antigen specific effector T cells for help

Question 8

How do T cells help B cells

Answer 8

T cells recognize peptide derived from antigen bound to BCR
Conjugated naive B cell and T cell exchange signals to initiate B cell activation

Question 9

After receiving T cell help, where does the first wave of B cells go?

Answer 9

Primary focus for expansion antigen activated B cells in the medullary cords

Question 10

Where does the second wave of B cells go?

Answer 10

Secondary focus for expansion of antigen activated B cells in the germinal center

Question 11

What is the difference between the antibodies each wave of B cells generates?

Answer 11

First wave generates plasma cells that secrete low affinity IgM
Second wave generates plasma cells that secrete high affinity class switched antibodies and memory cells

Question 12

What is a thymus independent antigen

Answer 12

Antigen that generates antibodies independent of T cells
Have repeating epitope that can strongly cross-link the BCR and coreceptor
Mostly generates low affinity IgM

Question 13

What is a germinal center

Answer 13

Generate high affinity plasma cells and memory B cells
Centroblasts: B cells that proliferate rapidly
Centrocytes: B cells that compete with one another for survival signals from FDCs

Question 14

What types pf signals from the Tfh cells drive isotype switching?

Answer 14

Cytokines (ILs, IFNs, TGF)

Question 15

What happens if there is a deficiency in CD40/Cd40L signaling?

Answer 15

Lymph nodes won’t form germinal centers
Cells will only generate IgM, called hyper IgM syndrome

Question 16

What are the short-term and long-term fates of B cells that receive T cell help?

Answer 16

Short lived: (first cells that exit germinal centers) plasma cells migrate to the bone marrow where they secrete antibodies
Long lived: (later during infection) B cells become memory B cells which go into circulation until the next time the antigen is encountered

Question 17

Memory B cells

Answer 17

Allow for faster response the second time the antigen is encountered
Have already undergone germinal center reaction, somatic hypermutation, and isotype switching
Can more quickly generate high affinity neutralizing antibodies than naive B cells