ASSOCIATION OF CD2 AND CD45 ON HUMAN LYMPHOCYTES-T

AT least two membrane receptors have been defined through which human T lymphocytes can be induced to proliferate and differentiate, namely the CD3-Ti antigen receptor complex1 and the CD2 molecule2. Monoclonal antibodies directed at either CD2 or CD3 induce intracellular second messenger production and subsequent protein phosphorylation3-5. On most human non-B lymphocytes, CD3-Ti and CD2 are coexpressed and seem to be functionally interrelated6. But there are minor subpopulations in which these receptor systems can transduce signals despite a mutually exclusive expression7,8, indicating that CD3-Ti and CD2 can act independently of each other. This view is supported by the finding that most monoclonal antibodies directed at the CD45 molecules9,10 are strongly co-mitogenic with CD2 but not CD3 monoclonal antibodies (refs 11,12). As the intracytoplasmic domains of CD45 have tyrosine phosphatase activity13 these functional effects11,12 could be explained by a physical association between CD2 and CD45. Using chemical crosslinking techniques, we now show that CD45 is linked to CD2 on the surface of human T lymphocytes. © 1990 Nature Publishing Group.