Expression of CII TA gene in five human malignant hematological cell lines and its significance.

The role of MHC class II transactivator (C II TA) in constitutive or IFN-gamma inducible expression of HLA molecules in human malignant hematological cell lines was investigated. The expression of HLA molecules and C II TA protein was detected by Western blot, immunohistochemistry and flow cytometry. The expression of C II TA gene was determined by RT-PCR. The capability of peripheral blood T cell reaction stimulated by tumor cells was monitored by mixed lymphocyte reaction. It was found that the HLAII-positive tumor cells expressed the C II TA quite well, and the expression of HLA I + II was increased in the tumor cells with constitutive or inducible expression of C II TA after induced by IFN-gamma. The tumor cells which did not express C II TA after induced by IFN-gamma were not response to the expression of HLA II promoted by IFN-gamma. It suggests a correlation between the inability of some malignant hematological cell lines in response to IFN-gamma for HLA expression and the deficiency in the inducible expression of C II TA, indicating C II TA might take part in the regulation of HLA I + II expression in the tumor cells, which might play an important role in tumor immunologic escape.