CTLA4 and melanoma: CTLA-4 also referred to as CD152 [23] is a co-inhibitory receptor expressed on the plasma membrane of activated cytotoxic T cells, helper T cells, T regs, memory T cells, natural killer cells [24], monocytes, granulocytes, B cells, skeletal muscle cells, placental fibroblasts [23] and in lung, bladder, ovarian, colon, renal, breast, uterine, rhabdomyosarcoma, melanoma and neuroblastoma cancer cell lines [25].