DR antigens expressed on tumor cells do not contribute to the blastogenetic response of autologous T cells.

Tumor cell suspensions prepared from surgical specimens were characterized for cellular composition and reactivity with monoclonal antibodies detecting T lymphocytes, monocytes, and the monomorphic determinants of DR molecules (antigens encoded by the D region of the major histocompatibility complex in man). About half the adenocarcinoma preparations contained tumor cells which expressed DR antigens. Lymphocytes of certain patients were stimulated in vitro by the autologous tumor cells, and this was independent of the expression of DR antigens on the tumor cells. In addition, pretreatment of the stimulator tumor cells with anti-DR Mab (monoclonal antibody) had only marginal effect on their stimulatory potential. In contrast, when the same tumor cells were used as stimulators of allogeneic lymphocytes, proliferation was more often seen with DR-positive tumors and the reaction was often inhibited by the anti-DR Mab treatment. There were exceptions, however, which suggest that other DR antigens not detected by the reagents used may have been expressed on these cells. The allostimulatory capacity of the tumor cells was usually weak and did not occur with all responder lymphocytes. It is important to note that stimulation of autologous lymphocytes could occur with tumor preparations that did not elicit allogeneic response. Thus, the in vitro stimulation of autologous blood-derived T cells by suspensions of unpropagated cells separated from solid tumors reflects the sensitization state of the patients against their tumor cells.