Tumor immunity to murine plasma cell tumors. VII. Expression of H-2 and tumor antigens on Ig synthesis variants of MPC-11.

As a part of our continuing investigations directed toward defining the nature of the antigens on murine plasmacytomas (PCT), MPC-11 and two immunoglobulin (Ig) synthesis variants of this cell line were examined for H-2 and tumor-associated antigen (TAA) expression, and for the possible role of H-2 in the cytotoxic T lymphocyte response to TAA. The tumor lines studied were MPC-11 (an IgG2b producer), MPC-11,662 (a variant which produces only light chains), and NP.2 (a variant which produces neither Ig chain). Both H-2 expression, which was analyzed by flow cytometry and by cold target cell blocking of the activity of cytotoxic T lymphocytes (CTL) generated in allogeneic cultures, and TAA expression, which was analyzed by cold target cell blocking of the activity of tumor-specific CTL generated in syngeneic cultures, were found to be quantitatively similar on the three lines. When a possible association between H-2 and TAA expression was examined by testing the ability of anti H-2 sera to block tumor-specific CTL directed against MPC-11, no association between H-2 and TAA was detected. The results of these studies provide new information about H-2 and TAA expression on murine PCT. Furthermore, they suggest that changes in H-2 and TAA expression which have been reported to sometimes accompany loss of Ig synthesis may represent independent genetic, phenotypic, or metabolic variations, rather than alterations linked to the loss of Ig synthesis. In addition, these results, in agreement with out previous studies on MPC-11, support the concept that there is not an obligatory association of TAA with H-2 on the surface of murine PCT. Because these results differ from those reported in some other systems in which an association between H-2 and TAA on murine PCT was demonstrated, it must be emphasized that the TAA of PCT appear to be quite heterogeneous, and more investigations will be necessary in order to clearly define these antigen and the T-cell response to each of them.