antibody diversity

What is the primary purpose of antibody diversity?

To generate a wide variety of antibodies that can recognize and neutralize a vast array of antigens

What are the five key mechanisms of antibody diversity?

• Combinatorial diversity.

• Junctional diversity.

• Somatic hypermutation (SHM).

• Class switch recombination (CSR).

• Combinatorial pairing of heavy and light chains.

What enzyme mediates V(D)J recombination during combinatorial diversity?

Recombination Activating Genes

How does junctional diversity enhance antibody variability

By adding N-nucleotides (via TdT) and P-nucleotides at the joining sites of V, D, and J segments during recombination

What process introduces point mutations into the V region of immunoglobulin genes in activated B cells?

Somatic hypermutation (SHM)

What enzyme is crucial for class switch recombination

Activation-Induced Cytidine Deaminase (AID).

Where does somatic hypermutation primarily occur

In the germinal centres of secondary lymphoid tissues.

What is the difference between affinity and avidity in antibody-antigen interactions?

• Affinity: The strength of binding between a single antigen-binding site and an epitope.

• Avidity: The overall binding strength between a multivalent antibody and a multivalent antigen.

What is the key difference between germline theory and somatic mutation theory regarding antibody diversity?

• Germline Theory: Suggests each antibody is encoded by a separate germline gene.

• Somatic Mutation Theory: Suggests a limited number of germline genes mutate somatically to generate diversity.

What are the two main loci for light chains in immunoglobulins?

• Kappa (κ) locus on chromosome 2.

• Lambda (λ) locus on chromosome 22.

How is T-cell receptor (TCR) diversity generated?

• Combinatorial diversity via V(D)J recombination.

• Junctional diversity through N-nucleotide addition by TdT

Why do TCRs not undergo somatic hypermutation?

To maintain constant antigen specificity and prevent autoimmunity.

Compare B-cell receptors (BCRs) and T-cell receptors (TCRs) in terms of effector function

• BCRs: Can directly neutralize antigens.

• TCRs: Require MHC presentation to recognize antigens.

What is the function of terminal deoxynucleotidyl transferase (TdT)?

Adds non-templated (N) nucleotides at V(D)J junctions during recombination, increasing diversity.

What is the role of germinal centres in the immune system?

sites within lymphoid tissues where B cells undergo somatic hypermutation, clonal selection, and class switching

What does the term "affinity maturation" refer to?

The process by which somatic hypermutation in B cells produces antibodies with higher affinity for an antigen.

How does class switch recombination (CSR) affect the antibody molecule?

It changes the constant region of the antibody's heavy chain, altering the isotype (e.g., IgM → IgG) while maintaining antigen specificity.

What are the two types of T-cell receptors

alpha beta TCR, gamma delta TCR