The CD4 (HIT4c) Antibody recognizes a 55 kDa type-I single-chain transmembrane glycoprotein. CD4 antigen is a coreceptor for HLA class II molecule and HIV (human immunodeficiency virus), which is present on 35-50% of peripheral blood lymphocytes-T helper/inducer (Th/Ti), 70-80% of thymocytes and in low density on the peripheral blood monocytes and tissue macrophages. Th/Ti helps Ig production by B lymphocytes by enhancing maturation and increasing effectiveness of cytoto, Xenopus/Amphibian,ic CD8 T cells.