B-cell memory and the persistence of antibody responses

Antigens such as viral envelope proteins and bacterial exotoxins induce res ponses which result in the production of neutralizing antibody. These respo nses persist for years and provide highly efficient defence against reinfec tion. During these antibody responses a proportion of participating B cells mutate the genes that encode their immunoglobulin variable regions. This c an increase the affinity of the antibody, but can also induce autoreactive B cells. Selection mechanisms operate which allow the cells with high affin ity for the provoking antigen to persist, while other B cells recruited int o the response die.