Recently, Jelcic and colleagues (94) have shown that memory B cells from HLADR15+ MS patients activate CD4 T cells in the absence of exogenous antigen and identified a peptide of RAS guanyl-releasing protein 2 (RASGRP2) as a self-peptide responsible for CD4 T cell activation. The gene discussed is RASGRP2; the disease is myeloid sarcoma.