What is T4 Antigens, T-Cell?

55-kD Glycoproteins originally defined as differentiation antigens on T-lymphocytes, but also found on other cells including monocytes/macrophages. CD4 antigens are members of the immunoglobulin supergene family and are implicated as associative recognition elements in MHC (Major Histocompatibility Complex) Class II-restricted immune responses. On T-lymphocytes they define the helper/inducer subset. CD4 antigens also serve as HIV receptors, binding directly to the envelope protein gp120 on HIV.