CD4 and colitis: To elucidate the mechanism by which diseased Crohn's mesentery tissue‐derived MSCs/EVs reduces pathogenic Th1/Th2/Th9/Th17/Treg responses and ameliorate disease severity in colitis, CD4+ T cells were isolated from naive WT mice and cultured under Th1/Th2/Th9/Th17/Treg polarization conditions.