Question

1) What receptor do T cells use to bind antigen? How is it similar to the receptor used by B cells? How is it different?

2.) How is TCR (T cell receptor) diversity achieved? How is it similar to Ig (immunogloblin) diversity? How is it different?

3.)What kinds of antigens and epitopes to TCR bind/recognize? How is it similar to the antigens/epitopes bound by Ig? How is it different

Answer 1

1) T cells use T-cell receptor (TCR) to bind antigen.

Both are structurally similar, both TCR and BCR are members of immunoglobulin superfamily and have Ig domain.

The B-cell receptors (BCRs) can bind to soluble antigens, where as T-cell receptors (TCRs) can only bind antigen that is complexed with MHC molecules on the surface of other cells.

2) TCR diversity arises from genetic recombination of the DNA segments in individual somatic T cells via somatic V(D)J recombination by using RAG1 and RAG2 recombinases.

This is similar to Ig diversity as that also arises from similar type of v(D)J recombination.

This is different from Ig because TCR genes do not go through somatic hypermutation, whereas Ig genes do the same.

3) TCR binds peptide epitopes bound with MHC molecules.

This is similar to the epitopes bound by Ig, as both of them can only bind a particular epitope portion of a peptide, not full peptide.

This is different from Ig, as TCR binds epitopes of a peptide that is only complexed with MHC molecule, whereas, Ig binds epitopes of free peptide molecule.