MPA abolishes B cell proliferation and plasma cell formation. Mycophenolic acid (MPA) completely abolishes CPG- or anti-CD40 +IL21-induced proliferation of CD27-antigen-naïve B cells (A) or CD27+ memory B cells (B). Results of a representative B cell proliferation assay of a healthy donor are shown. CD27-IgD+ B cells (A) or CD27+ B cells (B) were isolated, labeled with carboxy-fluorescein-succinimidyl ester (CFSE) and stimulated for 3 to 4 days as indicated. Gated on live cells, plasmablast gates are shown. Dividing-B cells lose CFSE with any cell division.