CD4 and urinary bladder neoplasm: Consistent with an active cell-mediated immunosuppressive TME, co-culturing CD45+ cells from MB49luc bladder tumors from control Ig–treated mice with splenic effector cells reduced the percentage of Ki67-expressing splenic CD4+ and CD8+ cells in response to αCD3/28 to 21.3 and 40.2%, respectively (Fig. 4a, left panels).