Molecular characterization of novel H-2 class I molecules expressed by a C3H UV-induced fibrosarcoma.

Two novel class I-like molecules expressed on tumor 1591, a C3H UV-induced fibrosarcoma, are biochemically characterized using two-dimensional gel electrophoresis, a cross-blocking RIA, and tryptic peptide mapping. One novel molecule that reacts with CP28, a syngeneic tumor-specific monoclonal antibody, appears mosaic because it possesses characteristics of both Kk and Dk class I molecules. The second molecule is closely related but not identical to the bona fide Ld molecule expressed on BALB/c spleen. Thus 1591 expresses at least two novel class I molecules and is vigorously rejected by normal C3H mice, while a variant tumor derived from 1591, termed AS7, does not express these two class I molecules although it still expresses Kk and Dk. The significance of these observations to the immunobiology and genetics of the UV-induced fibrosarcoma system is discussed. Speculations on the role that the major histocompatibility complex may play in the immunosurveillance of neoplasms are also presented.