Page 536 - Veterinary Immunology, 10th Edition

VetBooks.ir T Cell Receptor Diversity

TCR and immunoglobulin gene rearrangements are specific in that
immunoglobulin genes are not rearranged in T cells, and TCR genes

are not rearranged in B cells. Like immunoglobulins, the four
peptide chains, α, β, γ, and δ, that make up the two types of TCR
can bind many specific antigens. They are able to do this because
each consists of a variable region attached to a constant region. The
diversity of TCR V regions is generated exclusively by gene

recombination in contrast to the diverse mechanisms employed by
B cells.

T Cell Receptor Gene Structure

The four TCR peptide chains are coded for by three gene loci. The
TRA/D locus codes for both α and δ chains since the TRD genes are
embedded within the TRA locus. The TRB locus codes only for β
chains, and the TRG locus codes only for γ chains. All three TCR

loci contain V, J, and C genes, and the TRB and TRD loci also
contain D genes (Fig. 17.13).

FIG. 17.13 The basic structure of the three gene loci that code for
the four TCR chains. The genes for δ chains are embedded within

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