CD8 clone SK1 is derived from hybridization of mouse NS-1 myeloma cells with spleen cells from BALB/c mice immunized with human peripheral blood T lymphocytes.

The CD8 antibody recognizes the 32-kilodalton (kDa) -subunit of a disulfide-linked bimolecular complex. The majority of peripheral blood CD8+ T lymphocytes expresses an / heterodimer (Mr 32, 30 kDa), while CD8+CD16+ natural killer (NK) lymphocytes and CD8+ T-cell receptor (TCR)- / + T lymphocytes express an / homodimer (Mr 30 kDa). CD8+TCR- / + T lymphocytes can express either an / homodimer or / heterodimer. The CD8 antigenic determinant binds to class I major histocompatibility (MHC) molecules, resulting in increased adhesion between the CD8+ T lymphocytes and target cells. Binding of the CD8 antigen to class I MHC molecules enhances the activation of resting T lymphocytes. The CD8 antigen is coupled to a protein tyrosine kinase, p56lck. The CD8:p56lck complex can play a role in T-lymphocyte activation through mediation of the interactions between the CD8 antigen and the CD3/TCR complex.