Crosslinking CD81 results in activation of TCRγδ T cells

CD81 is expressed on most cells and is associated with other glycoproteins, including CD4 and CD8, to form multimolecular membrane complexes. Crosslinking of CD81 on TCR alpha beta (+) T cells results in costimulatory signals that have been proposed to be mediated via CD4 or CD8, In this study, we show that CD81 is also expressed on TCR gamma delta (+)CD4(-)CD8(-) T cells. CD81 crosslinking greatly enhanced anti-CD3 activation of both TCR alpha beta (+) (CD4(+) and CD8(+)) and TCR gamma delta (+) T cells with regard to IFN-gamma production. However, crosslinking of CD81 molecules on TCR gamma delta (+) T cells, in the absence of anti-CD3 stimulation, resulted in cytokine production and enhanced IL-a-induced proliferation, demonstrating that physical association with CD4 or CD8 is not necessary for CD81 signaling. In contrast, crosslinking of CD81 on TCR alpha beta (+) T cells, in the absence of anti-CD3 stimulation, failed to activate these T cells. These results suggest that CD81 signaling may be mediated via a different mechanism(s) in TCR gamma delta (+) versus TCR alpha beta (+) T cells. (C) 2001 Academic Press.