CD4 and major depressive disorder: Monocytes from UC patients with symptoms of anxiety/depression significantly inhibited CD4 + T cells from healthy volunteers polarized to Treg cells [1.37(0.68,2.34) vs. 2.40(2.15,4.56), P = 0.0124] (Fig. 3A), and induced CD4 + T cells to differentiate into Th1 cells [4.52(3.05,6.37) vs. 3.25(2.07,3.77), P = 0.0409] (Fig. 3B) contrasted to monocytes from UC patients without symptoms of anxiety/depression.