Lymphocyte activation antigens. I. A monoclonal antibody, anti-Act I, defines a new late lymphocyte activation antigen
Lazarovits, A.I.; Moscicki, R.A.; Kurnick, J.T.; Camerini, D.; Bhan, A.K.; Baird, L.G.; Erikson, M.; Colvin, R.B.
Journal of Immunology 133(4): 1857-1862
1984
ISSN/ISBN: 0022-1767 PMID: 6088627 Document Number: 238302
Lymphocyte activation entails a sequence of events identified by analyzing the time course of expression of various distinctive cell surface molecules on lymphocytes that appear early (before initiation of DNA synthesis), parallel with DNA synthesis and cellular proliferation, or late (after peak proliferation). This study identifies a novel late lymphocyte activation antigen, Act I, utilizing a murine monoclonal antibody. Anti-Act I was identified in a fusion of NS1 with BALB/c spleen cells immunized with a human tetanus toxoid-reactive T lymphoblast line. Flow cytometry analysis shows that Act I antigen is present is markedly greater amounts on activated T and B lymphocytes than in resting, small peripheral blood lymphocytes. Act I expression by these lymphocytes is promoted by phytohemagglutinin (PHA), tetanus toxoid or alloantigens, and lags behind maximal thymidine incorporation by 1-2 days. Thymocytes can be triggered to express Act I antigen during maturation induced by PHA/T cell growth factor stimulation. In vitro, anti-Act I does not affect antigen- or lectin-stimulated T cell proliferation. T cell-mediated lymphocytotoxicity or T cell growth factor-induced proliferation of T lymphoblasts. By immunoperoxidase analysis, Act I antigen is restricted to lymphoid tissue, staining many lymphocytes in the paracortex, germinal centers and mantle zones of lymph nodes, tonsil and spleen. By immunoprecipitation, the Act I antigen is a single band of 63,000 MW on reduced or nonreduced sodium dodecyl sulfate gels. The distribution, size, time course and functional correlates indicate that Act I is different from other known T cell activation markers detected with anti-Tac, OKT9, B3/25, OKT10, 4F2, CBL1 and anti=Ia-like antibodies. Although the function of Act I is still undetermined, it may serve as a useful marker of a late stage of activation in vitro and in vivo.