CD69 in resting and activated T lymphocytes. Its association with a GTP binding protein and biochemical requirements for its expression
Risso, A.; Smilovich, D.; Capra, M.C.; Baldissarro, I.; Yan, G.; Bargellesi, A.; Cosulich, M.E.
Journal of Immunology 146(12): 4105-4114
1991
ISSN/ISBN: 0022-1767 PMID: 1710239 Document Number: 384905
CD69 is a phosphorylated disulfide-linked homodimer that appears on the surface of human T, B cells and thymocytes in the early steps of activation; its molecular mass is 28 to 34 kDa under reducing conditions. This molecule is able to mediate positive signals to the lymphocytes as the anti-CD69 mAb (MLR3, AIM, Leu 23) in synergism with phorbol esters induce IL-2 production and proliferation of lymphocytes. Here we show that this molecule is associated to a GTP binding protein that is a substrate for Bordetella pertussis toxin. The relevance of CD69 in the activation process is also suggested by the broad range of signals able to modulate CD69 on T cells. In fact, not only the mitogens or the CD3-promoted activation, but also the alternative pathways mediated by CD2 or CD28 are accompanied by CD69 expression; moreover a very rapid and transient appearance of CD69 on the cell surface is observed also in response to a stimulus not specifically involved in T cell activation such as heat shock. Finally we demonstrate that CD69 is present in the cytoplasm of nonactivated T cells; accordingly its surface expression at the onset of activation is independent on a new RNA or protein synthesis.