Autoreactive B cells get activated in extrafollicular sites.

Autoreactive B cells are prevented from producing autoantibodies that may cause pathogenicity in autoimmune diseases by the induction of tolerance. When autoreactive B cells escape regulation in autoimmune-prone individuals, large amounts of autoantibodies are produced with somatic mutations in their variable regions. In this issue of the European Journal of Immunology, a new and very useful model is presented that induces activation and hypermutation of autoreactive B cells upon injection of chromatin-containing immune complexes. The differentiation and hypermutation of autoreactive B cells takes place at extrafollicular sites.