Monoclonal antibodies to murine leukemia virus gp 70 recognize the same T lymphoma cell surface molecules as anti-immunoglobulin.

Chicken antisera to mouse immunoglobulin (anti-Ig) detect molecules on T lymphocytes of mice consisting of "heavy chains" similar in size to IgM mu chains and "light chains" similar in size to lambda or kappa chains. Because these T cell-derived proteins react with anti-Ig and are composed of Ig-like heavy and light chains, these molecules have been viewed as candidates for "IgT," the putative T lymphocyte receptor for antigen. We have demonstrated, by immunoprecipitation and two-dimensional gel analysis, that the lymphoma surface molecule precipitated by chicken anti-Ig is identical to the viral 70,000 dalton glycoprotein (gp 70) expressed by that lymphoma and is unassociated with any "light chain" or equivalent. For each of the three lymphomas analyzed, the gp 70 two-dimensional gel pattern was individually distinctive, and, in each case, the molecules precipitated by anti-Ig exhibited the same pattern as the gp 70. The viral gp 70 does have cross-reacting determinants with mouse IgM as seen by the chicken antiserum. We have substantiated these results by demonstrating that monoclonal antibodies to viral gp 70 precipitate the same molecules as chicken anti-Ig. These findings demonstrate that these T lymphoma cell surface molecules do not represent the T cell immunoglobulin receptor for antigen unless gp 70 itself is an antigen receptor.