TBX21 and systemic lupus erythematosus: These data suggest that dysregulated apoptosis in B cells by loss of Bim promotes accumulation of autoreactive B cell populations and CD21loCD23lo B cells, which may be related to SLE-associated Tbet+ B cells (51), along with an increase in CD4 T effector and Tfh cells (Figures 2R, S) raise the possibility of autoimmune pathogenesis in BBimfl/fl mice.