CD4 and cancer: However, under various pathological inflammatory conditions such as cancer, infection, sepsis, graft-versus-host disease, and bone marrow transplantation, a variety of cytokines and soluble factors released induce rapid expansion of MDSC that will accumulate in peripheral lymphoid organs and blood, as well as in tumors, where they have been described to block CD4+ and CD8+ T-cell responses thus favoring cancer development [111].