CD4 and B cell deficiency: Breg inhibit proliferation of CD4+ TH1 cells by secretion of suppressive cytokines, such as IL-10 and TGF-β, and promote conversion of CD4+CD25− T cells to CD4+CD25+FoxP3+ Treg with high expression of CTLA-4 and FoxP3, and the anti-tumor effects of B cell deficiency has been shown to be mediated by enhanced T cell and NK cell infiltration, vigorous TH1 and CTL activity and reduced Treg proliferation (139).