Anti-CD4 antibodies are useful reagents for the immunodetection of the target protein, CD4. CD4 is a 51 kDa surface marker expressed on immune cells, including T helper cells, macrophages, dendritic cells, and NK cells. It functions as a coreceptor for the T-cell receptor (TCR) and the MHC class II complex. In humans, the CD4 gene encodes the protein 'CD4 molecule.' It may also be known as LEU3, IMD79, and OKT4D. CD4 is the primary receptor for the virus HIV-1. Antibodies to CD4 can be used to study signal transduction.