CD4 and neoplasm: •Exhaustion of T-cell and NK activities•Inhibit expansion of CD4+ and CD8+ T cells•Suppresses antigen-presenting cell activities and expression of antigen-presenting molecules and inflammatory cytokines•Inhibit B cell antibody production•Strongly promotes immunosuppressive tumor environment•Induces ATP catabolism•Secretes cytokines (IL-10, TGF-β, IL-35), immunosuppressive molecules (granzyme B, perforins)