Lecture 23 - Humoral Immunity

Question 1

What are the structural components of an antibody?

Answer 1

Fab region contains light chain and part of the heavy chain
Fc region contains contains heavy chains
Variable region is the top of the chains and contains antigen binding site
Constant region is the bottom regions

Question 2

What are 6 ways antibodies combat bacterial and viral infections?

Answer 2

1. Neutralization (block surface toxin or virus)
2. Interfere with pili and flagella
3. Agglutination (clump pathogens)
4. Opsonization (enhance phagocytosis)
5. Complement activation (classical pathway)
6. Tag for destruction (Fc attaches to NK cells)

Question 3

What are the 5 classes of antibodies?

Answer 3

1. IgG
2. IgA
3. IgM
4. IgE
5. IgD

Question 4

IgG

Answer 4

mainly found as a monomer in the serum, it plays roles in inflammation

Question 5

IgA

Answer 5

mainly found as a dimer in colostrum, it prevents infections

Question 6

IgM

Answer 6

a pentamer, first antibody produced during the primary immune response

Question 7

IgE

Answer 7

responsible for allergic/parasite response

Question 8

IgD

Answer 8

found on naive circulating B cells, it acts as B cell receptor and activates B cell cells

Question 9

What is “isotype (class) switching”?

Answer 9

It is when you switch the class of antibody produced by B cells
1. helper T cells release cytokine signals
2. B cells produce PTIP
3. PTIP switches heavy chain region
4. B cells produce IgG/IgA/IgE

Question 10

What does isotype switching involve?

Answer 10

immune memory

Question 11

What is the process of somatic recombination?

Answer 11

antibody genes are put together by combining parts
Heavy chain can have variable V,C, and J regions
Light chain can have variable V and J regions

Question 12

Somatic recombination occurs _________ B cell stimulation by an antigen. Why?

Answer 12

It occurs BEFORE so that the B cell does not “know” which antigen it is “supposed to” recognize

Question 13

How do TH cells activate B cells to produce antibodies?

Answer 13

1. B cell displays antigen from APC
2. The T cell receptor binds to the B cell MHCII. CD4 on T cell stabilizes interaction
3. CD40L of the activated TH cell is recognized by CD40 of the B cell
4. B cells divide and make clones
5. Clones turn into plasma cells which secrete antibodies

Question 14

What is the difference between T dependent and T-independent B cell responses?

Answer 14

T-independent activation has a weaker response, does not produce memory B cells, and does not undergo class switching (so only IgM)

Question 15

Vaccine designs

Answer 15

Protein-Conjugate: polysaccharide conjugated with MHCII, helper T cell recognize, T-dependent activation (memory B cell, class switching)
Polysaccharide Capsule: T-independent response

Question 16

What happens to prevent “self” recognizing B cells from becoming activated?

Answer 16

clonal deletion uses negative selection to eliminate
1. bone marrow: regulatory T cells check antigen of B cells, apoptosis
2. circulation: B cell is not activated by helper T cell, anergic, dies