TH2 cytokine expression from mesenteric lymph-node cells from immunized BCL-6 −/−, wild-type, BCL-6 −/− STAT6 −/−, and STAT6 −/− mice. Gray bars represent either wild-type, STAT6 −/−, or IL-4 −/− littermate controls; black bars represent either BCL-6 −/− STAT6 −/− or BCL-6 −/− IL-4 −/− double-mutant mice. Numbers at the top of the graph bars indicate n-fold increase of BCL-6 −/− or BCL-6 −/− STAT6 −/− cytokine levels over the highest levels obtained from control lymph-node cell stimulations. Cytokine units are ng/ml. N.D., not done.