Influence of class I H-2 gene expression on local tumor growth. Description of a model obtained from clones derived from a solid BALB/c tumor.

A BALB/c methylcholanthrene-induced tumor was studied for class I and II H-2 expression. GR9 was adapted to tissue culture without any passage in vivo to avoid immunoselection mechanisms. Forty-three clones were obtained and typed for H-2 antigens. A variety of techniques were used for typing, for example, 51Cr release assay, radiobinding assay; absorption with anti H-2 monoclonal antibodies or H-2 allo-antisera and alloreacting cytotoxic T lymphocytes. A heterogeneity of H-2 expression was detected in these clones with clones H-2 K+/D+, to clones H-2K-D-. This heterogeneity was also evident when several GR9 clones were tested for in vivo growth in syngeneic BALB/c mice. Two clones, A7 and B9, were selected for further studies and injected into syngeneic animals to measure local tumor growth. A7 (K+/D+) was rather immunogenic while B9 (K-/D-) was not. These differences were probably due to an immunoresponse, since both clones grow similarly in irradiated syngeneic BALB/c mice. Immunoprecipitations of H-2 antigens and SDS-PAGE analysis confirmed the results obtained in serology. Three isoenzymes were also determined in GR9 clones and their electrophoretic mobility was always identical to that obtained in normal BALB/c tissues. These results suggest that K and D molecules are important structures for an immunoresponse against tumor-associated antigens.