Antigen Receptor Diversity

What is germline DNA?

The hereditary material passed to offspring, not altered by somatic mutation.

What are the main types of antigen receptor genes?

Immunoglobulin (Ig) heavy (H) and light (L) chain genes, and T-cell receptor (TCR) alpha (a) and beta (b) chain genes.

What is gene recombination?

The rearrangement of DNA sequences to create new gene combinations.

How are junctional diversity and somatic hypermutation related to receptor diversity?

Junctional diversity introduces variability at gene segment junctions during recombination, while somatic hypermutation leads to mutations in B cells after antigen exposure, enhancing antibody affinity.

What is allelic exclusion?

The mechanism whereby only one allele of a gene is expressed while the other is silenced.

Describe the process of receptor editing in B cells.

A process by which B cells can modify their receptors to alter binding specificity, often in response to autoreactivity.

What types of recombination occur during immunoglobulin heavy chain gene rearrangement?

D-J rearrangement and V-DJ rearrangement.

What role do RAG-1 and RAG-2 proteins play in gene rearrangement?

They facilitate DNA cutting at specific signal sequences during the rearrangement processes.

What stimulates the generation of antibodies after immunization?

The process of gene rearrangement and selection of B cell clones, allowing for production against specific immunogens.

What is junctional diversity and how is it achieved?

Random addition of nucleotides at recombination sites during gene rearrangement, expressed through various B cell clones.

What happens during somatic hypermutation?

Point mutations occur in CDR regions of antibodies, enhancing the affinity for antigens following exposure.

How does T cell receptor (TCR) diversity compare to immunoglobulin diversity?

TCR diversity is generated through similar mechanisms of gene rearrangement (V(D)J recombination) and combinatorial uses of TCR alpha and beta chains.

What is the significance of the complementarity determining regions (CDR)?

They are located in the variable region and are crucial for determining the binding specificity of antibodies.

What is the range of distinct immunoglobulin or T cell receptor molecules each person can generate?

Between 10^15 to 10^18 distinct molecules.

What happens to B cells that do not successfully edit their receptors to correct autoreactivity?

They undergo apoptosis.