CD19 and Autoimmunity: Positive studies: increased numbers of CD21+, CD19+, activated CD5+, and CD24+ B cells (243, 303–305). Gene expression pattern suggesting impaired B cell differentiation and survival (306). Increased levels of B lymphocyte activating factor (307). Increased frequency of HLA alleles associated with autoimmunity (DQB1, KIR3DL1, and KIRDS1) (308–310). Antigen-driven clonal B cell expansion (311, 312).