Question

What are the genes of the B cell receptor on variable region? and what are the genes expressed in T cell receptors variable ?

Answer 1

Genes of B- Cell receptor :

T{he B-cell receptor resembles that of an immunoglobulin structure. For both the genes encoding the variable and constant regions are same. The light chain genes can be of two types - kappa and lambda. The kappa gene is located in chromosome 2 of humans. It has approximately 40 V rgenes, 5 J gene segments between V and C segment and it has a single C gene segment.

The lambda gene is located in Chromosome 22 of humans. It is composed of 4 Constant regions and around 30 Variable regions. The V genes are arranged linearly with each V exon being preceded by a leader exons. All the V segments are separated from each other by introns.

Genes of T-cell receptor :

Genes coding for the T-cell receptor are very similar to that of immunoglobulin genes. T-cell receptor genes have the same variable (V), diversity (D) , joining (J) gene segments and constant (C) genes. The TCRα locous located on Chromosome 14 has 70 - 80 V gene segments with an exon encoding the leader sequence present before each of them. It conists of 61 J alpha gene segments . The J alpha gene segments are then followed by a single C gene .

In case of TCRβ , the genes encoding for the receptor are present in Chromosome 7. It has a group or cluster of 52 V beta gene segments . The cluster of V beta gene segments are located far away from two other clusters - one of with a single D gene segment interspersed with 6-7 J beta gene segments and another of single C gene.