Cell-cell adhesion mediated by CD8 and MHC class I molecules

CD4 and CDS are cell-surface glycoproteins expressed on mutually exclusive subsets of peripheral T cells. T cells that express CD4 have T-cell antigen receptors that are specific for antigens presented by major histocompatibility complex class II molecules, whereas T cells that express CDS have receptors specific for antigens presented by MHC class I molecules (reviewed in ref. 1). Based on this correlation and on the observation that anti-CD4 and anti-CDS antibodies inhibit T-cell function, it has been suggested that CD4 and CDS increase the avidity of T cells for their targets by binding to MHC class II or MHC class I molecules respectively2,3. Also, CD4 and CDS may become physically associated with the T-cell antigen receptor, forming a higher-affinity complex for antigen and MHC molecules4–8, and could be involved in signal transduction5,6,9,10. Cell-cell adhesion dependent CD4 and MHC II molecules has recently been demonstrated11. To determine whether CDS can interact with MHC class I molecules in the absence of the T-cell antigen receptor, we have developed a cell-cell binding assay that measures adhesion of human B-cell lines expressing MHC class I molecules to transfected cells expressing high levels of human CDS. In this system, CDS and class I molecules mediate cell-cell adhesion, showing that CDS directly binds to MHC class I molecules.