Abstract
The effects of recombinant interferon gamma (IFN‐γ) 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 (AIAb). 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‐γ, HLA class‐II antigen was surface‐expressed on a small subpopulation of HEp‐2 only. All cell lines examined, except AIAb, could be induced to cell‐surface expression of HLA class‐II antigen after 48 hr incubation in the presence of IFN‐γ (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 ^3^H‐thymidine and ^3^H‐leucine and expression of the transferrin receptor were not significantly altered by IFN‐γ application, indicating a specific regulatory effect of IFN‐γ on HLA antigen expression. Our data demonstrate that HLA class‐II surface expression is inducible by IFN‐γ in a variety of epithelial tumor lines. This may have implications for the host immune system defense mechanisms against tumors.