Expression of H-2 and viral antigens and resistance to the antitumor lysis of tunicamycin-treated MBL-2 lymphoma cells

The role of protein glycosilation in the tumor lysis mediated by effector cells derived from Moloney-sarcoma-virus(MSV)-immune mice was studied. Treatment of the Moloney-virus-induced H-2^b lymphoma target cells, MBL-2, with tunicamycin (TM), an inhibitor of the protein-N-linked glycosilation, was found to cause a loss of susceptibility to lysis by MSV-immune syngeneic effector cells, while the same target cells remained fully sensitive to the lytic action of anti-H-2^b-immune lymphocytes. Examination of MBL-2 cell surface by lactoperoxidase, ¹²⁵I iodination, and immunoprecipitation by antiviral protein sera revealed that env but not gag viral gene-encoded products were expressed on the surface of this lymphoma. The TM-induced alteration of cell surface expression of H-2D^b, H-2K^b, and gp70 antigens was examined by a combined approach of serological and biochemical techniques. The results were concordant in indicating that (1) after 16 h of TM treatment the cells showed a decreased expression of the three glycoproteins, (2) H-2D^b (the restriction element in this system) resulted more affected by the treatment than its counterpart H-2K^b (75% vs 50% reduction as compared to untreated cells), (3) an additional lighter form of H-2K^b was found on the surface of TM-treated cells. In the contrast of an 'associative recognition' of D^b and gp70 by MSV-immune effector cells, our results may explain the loss of susceptibility to antitumor effectors of TM-treated MBL-2 cells by a quantitative reduction in the expression of both molecules which interact to create the target structure of syngeneic effectors.