Nuclear Organisation of Immunoglobulin Genes

Abstract

The function of a B cell is to produce antibodies which can respond to the numerous foreign antigens which we encounter. Since there are only a limited number of immunoglobulin genes (Ig) this is achieved through a process whereby variable (V), diversity (D) and joining (J) gene segments of immunoglobulin genes are rearranged in different orders to achieve antibodies with a vast range of different specificities. V(D)J recombination occurs in a lineage specific and developmentally regulated manner in the bone marrow. Since rearrangement takes place on both alleles at the same time during B cell development, as soon as a successful rearrangement is achieved on one of these alleles the other allele has to be prevented from continuing to rearrange. Allelic exclusion thus simplifies the problem of immune recognition by ensuring that only one of the two alleles is functionally rearranged so that each B cell makes antibodies that recognise a single target.