Objective: To investigate the role of major histocompatibility complex (MHC) II transactivator in constitutive or interferon (IFN)-gamma inducible expression of MHC molecules in human malignant hematological cell lines.
Methods: The expression of MHC molecules and MHC class II transactivator (CIITA) protein were detected with Western blot, immunohistochemistry and flow cytometry. The expression of CIITA gene was determined with RT-PCR. T cell expressing interleukin (IL)-2 mRNA was induced by Jurkat with mixed lymphocyte reaction.
Results: It was found that the MHCII-positive tumor cells expressed the CIITA quite well, and IFN-gamma could induce the expression of MHCI + II only if the tumor cells were able to express CIITA in an IFN-gamma induced manner (20%, 42% for Jurkat cells respectively), while T cell expressed more IL-2 mRNA (51 times) in the case of Jurkat after induction with IFN-gamma.
Conclusions: It is suggested that there is a correlation between the inability of the tumor cells in response to IFN-gamma for MHC expression and the deficiency in the inducible expression of CIITA. This might be due to immune sneaking through the tumor cells to some extent.