To study the role of Maf in T cells, we generated CD4creMaffl/fl mice (MafΔTcells), in which all T cells (CD4+ and CD8+) are inactivated for the expression of Maf. Interestingly, these mice spontaneously developed strong colitis, associated with a defect in weight gain starting at 16 weeks of age (Fig. 1A), concomitant with the appearance of diarrhea. The gene discussed is CD4; the disease is colitis.