Abstract
Spleen cells from Balb/c CRGL mice bearing the syngeneic chemically induced D1-DMBA-3 mammary adenocarcinoma exhibit an elevated blastogenic response to the mitogens PHA and Con A when compared to normal mice. Purified tumor cell membranes prepared by LiCl aggregation and sucrose density centrifugation are able to induce tumor associated antigen (TAA) specific blast transformation in tumor bearing animals. Both the mitogen and TAA induced blast transformation diminish with increasing tumor burden.Monodispersed tumor cell suspensions were prepared by enzyme digestion. The in situ lymphocytes (ISL) were isolated using centrifugal elutriation (CE). When the ISL were analysed for cell surface markers, they were found to be more than 90% Thy 1.2+ and less than 10% SIg+. Analysis of T cell subpopulations using monoclonal Lyt antibodies revealed a decrease in the Lyt 1.2+ subpopulation in the spleen and ISL when compared to normal. In contrast, the ISL showed a significant rise in the levels of Lyt 2.2+ lymphocytes.When the functional abilities of the ISL were examined with mitogen and TAA induced blast transformation, it was found that ISL did respond to both PHA and Con A, but never at levels seen in spleen cells. In contrast to the spleen cells of tumor bearers, ISL fail to respond to TAA at any stage of disease.To determine if this failure to respond was due to suppressor cells, the ISL were mixed with spleen cells and then tested for their ability to respond in mitogen or TAA induced blastogenesis. ISL were able to significantly depress both mitogen and TAA induced blast transformation in tumor bearer spleen cells. Removal of macrophages by Sephadex G-10 columns did not alter the suppression. Killing with Lyt antisera plus complement revealed that a Thy 1.2+, Lyt 2.2+ ISL was responsible for the suppression of both mitogen and TAA induced blast transformation.