Previous studies implicate insulin-reactive B cells in human T1D as antigen-presenting cells (APC) that promote autoreactive CD4+ and CD8+ T cell activation, based on immunophenotyping of peripheral blood and pancreatic islets of deceased T1D subjects of all ages, especially those < 7 years (2, 8–17). The gene discussed is CD4; the disease is type 1 diabetes mellitus.