V(D)J Recombination - in T Cell Receptors

In T Cell Receptors

During thymocyte development, the T cell receptor (TCR) chains undergo essentially the same sequence of ordered recombination events as that described for immunoglobulins. D-to-J recombination occurs first in the β chain of the TCR. This process can involve either the joining of the D_β1 gene segment to one of six J_β1 segments or the joining of the D_β2 gene segment to one of seven J_β2 segments. DJ recombination is followed (as above) with V_β-to-D_βJ_β rearrangements. All genes between the V_β-D_β-J_β genes in the newly formed complex are deleted and the primary transcript is synthesized that incorporates the constant domain gene (V_β-D_β-J_β-C_β). mRNA transcription splices out any intervening sequence and allows translation of the full length protein for the TCR C_β chain.

The rearrangement of the alpha (α) chain of the TCR follows β chain rearrangement, and resembles V-to-J rearrangement described for Ig light chains (see above). The assembly of the β- and α- chains results in formation of the αβ-TCR that is expressed on a majority of T cells.