The immunoglobulin variable-region gene repertoire and its analysis

Immunoglobulin (Ig) is a protein that binds to molecular determinants (antigens) on pathogenic microbes, infected cells, and dysregulated self. It serves as the recognition element of the B-cell receptor (BCR) and as secreted antibody, one of the key effectors of immunity. The domain of the Ig gene responsible for these functions is called the immunoglobulin variable region gene (IgVRG). The IgVRG repertoire-the collection of all IgVRGs simultaneously present in an individual organism-is diverse and dynamic. This diversity is due to the assembly of IgVRG by stochastic recombination of gene-segment libraries early in B-cell ontogeny and to somatic hypermutation subsequent to antigen exposure. B cells are activated by engagement of their BCR and proliferate, forming clones that undergo affinity maturation by somatic hypermutation and differentiate into long-lived plasma or memory cells. Affinity maturation is essential to effective humoral immunity; its induction is a primary goal of much vaccine design and in particular of vaccine design against human immunodeficiency virus 1 (HIV-1) disease.