A role in transmembrane signaling for the cytoplasmic domain of the CD2 T lymphocyte surface antigen.

The CD2 antigen can mediate mitogenesis of T lymphocytes after binding combinations of monoclonal antibodies. To examine the importance of the cytoplasmic domain in signaling, rat CD2 cDNA has been transfected into the human Jurkat cell line and triggering of an increase in cytoplasmic free Ca2+ concentration [( Ca2+]i) has been assayed. In cells expressing full-length CD2, a clear signal was triggered with anti-CD2 monoclonal antibodies. In contrast, a barely detectable increase in [Ca2+]i occurred with mutant rat CD2 molecules that included only 6 or 40 amino acids of the full-length cytoplasmic domain of 116 residues. It thus appears that the CD2 cytoplasmic domain plays a role in the signaling event.