MODULATION BY CANINE INTERFERON-GAMMA OF MAJOR HISTOCOMPATIBILITY COMPLEX AND TUMOR-ASSOCIATED ANTIGEN EXPRESSION IN CANINE MAMMARY-TUMOR AND MELANOMA CELL-LINES

In an effort to enhance the antigenicity of canine tumor cells, canine interferon-gamma (CnIFN-gamma) was applied in vitro to seven canine m ammary tumor (CMT) and two canine melanoma (CML) cell lines. Surface e xpression of major histocompatibility complex (MHC) antigens and tumor associated antigens (TAA) was measured by a flow cytometric fluoresce nce assay using commercially available anti-MHC antibodies, and anti-c anine TAA monoclonal antibodies generated against CMT and CML cell lin es. Compared to constitutive antigen levels in untreated cells, treatm ent with CnIFN-gamma resulted in increased expression of MHC class I a nd II antigens (up To 19-and 167-fold, respectively) and a TAA (up to 5-fold) by CMT cell lines, and increased expression of class I antigen (131-fold) by one CML and of class II antigen (18-fold) by the other CML cell line. Expression of MHC antigens and a TAA by tumor cells was increased by Cn-IFN-gamma treatment, and such an increase may be of p otential benefit in tumor cell recognition and rejection by the immune system.