T cell recognition of Moloney sarcoma virus proteins. II. Phenotypes of the different lymphocyte subpopulations producing and responding to blastogenic factors and their relative frequencies during tumor regression.

The characteristics of the blastogenic response of splenic lymphocytes from MoLV/MSV immune mice was examined. Splenic lymphocytes from immune mice proliferate in vitro in response to the major virion envelope glycoprotein, gp70. Associated with this response is production of blastogenic factors that induce the proliferation of nylon wool-purified lymphocytes from either normal or immune mice. The phenotype of antigen-specific lymphocytes essential for the production of blastogenic factors was found to be Thy 1.2+, Lyt 1+, 2-. The induction of proliferation by blastogenic factors does not require the presence of antigen. Using splenic lymphocytes from either normal or immune mice, blastogenic factors predominantly induce the proliferation of a Thy 1.2-, Lyt 1-, 2- lymphocyte. As a consequence of responding to blastogenic factors, in vitro, approximately 50% of this lymphocyte population becomes Thy 1.2+, Lyt 1+ over a period of 3 days. The frequencies of lymphocytes producing and responding to blastogenic factors were found to show characteristic changes during the course of tumor growth and regression.