Induction of HLA class-II antigen expression on human carcinoma cell lines by IFN-Gamma

The effects of recombinant interferon gamma (IFN-gamma) on HLA antigen expression were examined in various human carcinoma cell lines: carcinomas of the lung (ChaGo, Oat 75, SK-LC-LL), colon (HT-29, WiDr), larynx (HEp-2), cervix (ME-180) and mammary gland (AlAb). Surface expression of HLA antigens was determined using monoclonal antibodies directed against monomorphic determinants of HLA class II (HD II, 2.06) and HLA class I (W6/32) by several techniques including indirect immunofluorescence, immunoperoxidase assay, radioimmunoassay of cells, and immunoprecipitation of radioiodinated cells. Without previous exposure to IFN-gamma, HLA class-II antigen was surface-expressed on a small subpopulation of HEp-2 only. All cell lines examined, except AlAb, could be induced to cell-surface expression of HLA class-II antigen after 48 hr incubation in the presence of IFN-gamma (10 units/ml). HLA class-I antigen was present on all cell lines even without treatment, and it was increased after IFN-exposure. Incorporation of 3H-thymidine and 3H-leucine and expression of the transferrin receptor were not significantly altered by IFN-gamma application, indicating a specific regulatory effect of IFN-gamma on HLA antigen expression. Our data demonstrate that HLA class-II surface expression is inducible by IFN-gamma in a variety of epithelial tumor lines. This may have implications for the host immune system defense mechanisms against tumors.