0506 - B cells and antibodies - EG

Question 1

What are antibodies?

Answer 1

immunoglobulin proteins secreted by activated B cells (plasma cells), the same unique protein is also present on the B cell surface (each B cell has a unique protein)

Question 2

Define affinity.

Answer 2

The binding strength between the antibody and antigen at a single binding site.

Question 3

Define avidity.

Answer 3

The binding strength of an antibody and antigen at a number of binding sites.

Question 4

Describe the structure of an antibody.

Answer 4

Two chains, a heavy chain and a light chain. both have a variable, V, and constant, C, region, however the C region of the heavy chain is longer so as to either create a tail in free antigens or to embed in the plasma membrane on the surface of B cells. The variable region determines antibody specificity.

Question 5

What is found within the variable region?

Answer 5

complementarity determining regions (CDRs) that determine specificity of the antibody to an antigen.

Question 6

What is the function of IgG?

Answer 6

opsonisation of antigens for phagocytosis by macrophages and neutrophils, activation of classical pathway of complement.

Question 7

What is the function of IgM?

Answer 7

Activation of the classical pathway of complement, but more niave antigen receptors.

Question 8

What is the function of IgA?

Answer 8

Mucosal immunity, found in lumens of GI and respiratory. activation of complement by the lectin or by alternative pathway.

Question 9

What is the function of IgE?

Answer 9

mast cell degranulation

Question 10

Which immunoglobulin type activates the classical pathway of complement?

Answer 10

IgG and IgM.

Question 11

Which immunoglobulin type activates the lectin or alternative pathway of complement?

Answer 11

IgA

Question 12

Which immunoglobulin type forms a pentamer?

Answer 12

IgM

Question 13

Which immunoglobulin type forms a dimer?

Answer 13

IgA

Question 14

Which immuloglobulin types predominate in serum?

Answer 14

IgG and IgM

Question 15

What is somatic hypermutation?

Answer 15

The process by which germinal centre B cells mutate their B cell receptor to increase its affinity to an antigen by random mutations, the advantageous of which are known as affinity maturation.

Question 16

After activation of a B cell by a T cell, what are the 2 outcomes for the B cell?

Answer 16

Migration to extrafollicular area to become plasmablasts and plasma cells and secrete antibodies and migration to follicle to proliferate into a germinal centre and make a higher quality antibody (somatic hypermutation)

Question 17

Describe Thymus dependent antibody synthesis.

Answer 17

T:B cell interaction, antibody synthesis in response to protein antigens and formation of memory B cells.

Question 18

Describe T-independent B cell responses.

Answer 18

the absence of T cells, but activation of B cells occurs due to cross-linking of multiple B cell receptors.