Previous studies have demonstrated that the level of ROS in the CD4+ T‐cells increases after in vitro treatment with the cell‐free ascites.6 Additionally, incubation with the cell‐free ascites also enhances the ROS level in DCs, which induces ER stress and subsequently impairs the antigen‐presenting capacity of DCs and inhibits T‐cell activation.70 Moreover, the MDSCs and Tregs accumulate in the ovarian cancer ascites. Here, CD4 is linked to ovarian cancer.