In vitro and in vivo adoptive transfer experiments initially showed that different populations of murine-activated B cells are able to suppress antigen-specific CD4+ T cell proliferation and pro-inflammatory cytokine production in an IL-10-dependent manner and reduce inflammation in autoimmunity models, such as CIA (3, 23, 25, 36, 197), antigen-induced arthritis (11, 14, 21, 113), spontaneous lupus (94), type 1 diabetes (198), colitis (42), and EAE (10, 57, 70, 105, 199). The gene discussed is CD4; the disease is systemic lupus erythematosus.