T-cell surface antigen CD4 (IPR000973)

Short name: CD4

Overlapping homologous superfamilies


Family relationships



CD4 is a glycoprotein found on the surface of T cells. It is a co-receptor that assists the T cell receptor (TCR) in communicating with an antigen-presenting cell (APC). The structure of a soluble fragment of CD4 has been determined to 2.3 A and reveals that the molecule has two intimately-associated immunoglobulin-like domains connected by a continuous beta strand. Residues implicated in HIV recognition reside in domain D1. Domain D2 is distinguished by a variation in the beta-strand topologies of antibody domains that results in a truncated beta-barrel with a non-standard intra-sheet disulphide bond [PMID: 2247146, PMID: 1701030]. The binding sites for monoclonal antibodies, class II major histocompatibility complex molecules, and HIV gp120 can be mapped on the molecular surface.

GO terms

Biological Process

GO:0006955 immune response

Molecular Function

GO:0015026 coreceptor activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.