Affinity maturation

In immunology, affinity maturation is the process by which T_FH cell-activated B cells produce antibodies with increased affinity for antigen during the course of an immune response. With repeated exposures to the same antigen, a host will produce antibodies of successively greater affinities. A secondary response can elicit antibodies with several fold greater affinity than in a primary response. Affinity maturation primarily occurs on membrane immunoglobulin of germinal center B cells and as a direct result of somatic hypermutation (SHM) and selection by T_FH cells.

Affinity maturation also occurs when GC B cells encounter antigens related to the original antigen they were raised against, as long as some binding capabilities remain against the new variant antigen. Over many rounds of maturation against new variants, GC B cells could (very rarely) end up producing broadly-neutralizing antibodies that bind the common (conserved) part of these antigens. One ideal in the field of vaccination is to reliably replicate this process so as to immunize against a broad spectrum of related pathogens.