CD 8

Accurate, Ancell (UCHT4), Becton Dickinson (Leu2), Biodesign (UCHT4, CD8.C12, B9.11, B9.2), Biogenex (T8), Biotest (Tu102), Biogenesis (T80C), Caltag, Coulter (T8), Cymbus Bioscience (UCHT4), Dako (DK25, C8/144B), Exalpha, GenTrak, Immunotech (B9.2, B9.11), Oncogene (UCHT4), Pharmingen (RPA-Y8), Research Diagnostics (CLB-T8/4, UCHT4), Sanbio (MEM31, BLT58/2), Seralab (UCHT4) and Serotec (BHT, MF8).

Fresh-frozen section and fresh cytological preparations. Clone C8/144B is also immunoreactive in fixed paraffin-embedded tissue sections following HIER.

Like CD 4, the CD 8 molecule is composed of non-polymorphic glycoproteins, belonging to the Ig superfamily, that are expressed on the surface membrane of mutually exclusive, functionally distinct T-cell populations. The CD 8 molecule is a 34 kD glycoprotein that forms disulfide-linked homodimers and homomultimers on the cell surface of peripheral T-cells, the CD 8 gene being linked to thek locus on chromosome 2. The CD 8 molecule comprises an external domain and highly conserved transmembrane and intracellular domains, the external domain showing striking homology with other members of the Ig gene superfamily (Eichmann et al, 1989). The CD 8 molecule functions as a TCR coreceptor on suppressor/cytotoxic T-cells and recognizes foreign antigens as peptides presented by MHC class I molecules. In the thymus, the CD 8 molecule forms complexes with the CD 1 glycoprotein, an MHC class I-like molecule. CD 8 appears to bind to the non-polymorphic regions of MHC class I molecules and may thus serve to enhance the avidity of cell-to-cell interactions (Christinck et al, 1991). Both CD 4 and CD 8 antigens appear during the common thymocyte stage of T-cell differentiation and CD 8 is expressed by about 80% of normal thymocytes. Thereafter, CD 4 and CD 8 are retained by those maturing thymocytes destined to become helper/inducer and suppressor/cytotoxic T-cells respectively, CD 8 being expressed by about 25-35% of peripheral T-cells, specifically of the suppressor/cytotoxic subset (Martz et al, 1982). In addition, about 30% of NK cells express low levels of CD 8. This phenotypic-functional association is not universal and subpopulations of suppressor/cytotoxic T cells can be identified among CD 4+ cells (Parnes, 1989).

As with the CD 4 marker, CD 8 has an important role in the immunophenotypic analysis of reactive and neoplastic populations of T-cells, being used to identify a mature T-cell subset with suppressor/cytotoxic function. Like the CD 4 marker, CD 8 may also be aberrantly deleted from neoplastic T-cells. It is expressed on T-cell lymphoblastic lymphomas (Picker et al, 1987).

With the exception of clone C8/144B, most anti-CD8 antibodies are only immunoreactive in fresh-frozen sections and cytologic preparations.

•Christinck ER, Luscher MA, Barber BH, Williams DB 1991. Peptide binding class I MHC on living cells and quantitation of complexes required for CTL lysis. Nature 352: 67-70.

•Eichmann K, Boyce NW, Schmidt UR, Jonsson JI 1989. Distinct functions of CD8 (CD4) are utilised at different stages of T lymphocyte differentiation. Immunological Reviews 109: 39-75.

•Martz E, Davignon D, Kurzinger K, Springer TA 1982. The molecular basis for cytotoxic T lymphocyte function: analysis with blocking monoclonal antibodies. Advances in Experimental Medicine and Biology 146: 447-465.

•Parnes JR 1989. Molecular biology and function of CD4 and CD8. Advances in Immunology 44: 265-311.

•Picker LJ, Weiss LM, Medeiros JL et al 1987. Immunophenotypic criteria for the diagnosis of non-Hodgkin's lymphoma. American Journal of Pathology 128: 181-201.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.