A total of 5,634 genes were differentially expressed between anti-Yo PCD ovarian tumors and control ovarian tumors; among these genes, two members of the CD28 family—CTLA4 and ICOS—were significantly down-regulated, implying that suppressive functions of T cells could be altered within the anti-Yo PCD ovarian tumor microenvironment (114). This evidence concerns the gene ICOS and ovarian neoplasm.