Foundations of Immunology III

Question 1

How many heavy and light chains make up a B-cell antigen receptor?

Answer 1

Two heavy chains and two light chains

Question 2

What is the purpose of the fab region and the fc region?

Answer 2

The fab region binds the antigen

The Fc region defines the isotype, binds complement and attaches the B-cell to the plasma membrane

Question 3

What is somatic recombination? What system mediates its actions? What are two key genes?

Answer 3

Somatic recombination is the process by which the genes for the heavy and light chains can be spliced in a multitude of ways to introduce genetic diversity.

The V(D)J recombinase system regulates this process, and the recombinase activating genes RAG-1 and RAG-2 are very important

Question 4

What is allelic exclusion and why is it important?

Answer 4

It is the process that ensures that an B-cell only expresses one L-chain isotype and therefore only one antibody

This added specificity helps control the immune response

Question 5

What is the difference between somatic hypermutation and somatic recombination

Answer 5

Unlike somatic recombination, somatic hypermutation is antigen driven.

Note it results in a new mutation every 2/3 cell divisions.

Question 6

What is the difference between combinational and junctional diversity?

Answer 6

Combinational diversity is the different combination of V(D)J genes possible for different receptor specificities

Junctional diversity is the addition or subtraction of nucleotides at the joints between different gene segments

Question 7

Which region of the TCR recognizes an antigen?

Answer 7

The variable region

Question 8

What are the two types of TCR’s? Are they heterodimers or homodimers?

Answer 8

The two types of TCR’s are ab and GD. Both are heterodimers