A study in MRL/MpSlac-lpr mice with systemic autoimmune symptoms similar to human SLE analyzed prednisone action on plasma cell differentiation with regard to the impact of regulatory factors, including IL-21, Blimp-1, and Bcl-6 (B cell lymphoma-6—essential for germinal center development). The gene discussed is PRDM1; the disease is systemic lupus erythematosus.