Ig secretion by GC B cells cultured with cytokine combinations. Ig concentration was measured in the supernatant of GC B cells cultured for 10 days with CD32-L cells and cytokine combinations in the presence (▨) or absence (□) of CD40 MoAb, G28-5. (A) IgM; (B) IgA; (C) IgG1; (D) IgG2; (E) IgG3; (F ) IgG4.