CD4 and neoplasm: The functions of B7-H4 in immune escape are achieved mainly through the following three ways: (1) B7-H4-Ig fusion protein could activate regulatory T cells (Tregs), and then inhibit the proliferation and cytokine production of CD4+ and CD8+ T cells [30]; (2) B7-H4 could reduce the T-cell-stimulating capacity of macrophages, and then suppress tumor-associated antigen-specific T-cell immunity [31]; (3) B7-H4 could arrest cell cycle progression of cytotoxic T lymphocytes (CTLs) in G0/G1 phase [32].