Down Regulation of Qa Gene Expression on Drug-Modified Tumor Cells

Abstract

Background Mouse leukemia, L1210, strongly enhances its immunogenicity following in vivo treatment with 5-(3-3′-dimethyl-1-triazeno) imidazole-4-carboxamide (DTIC). Previous experiments have shown that transformed cells elicit a cell-mediated response accountable for rejection and resistance to a subsequent injection of parental tumor into a syngeneic host. L1210 expresses classical H-2 class I molecules, and since it has been shown that DTIC treatment does not modify the expression of these molecules, this is a suitable model to study nonclassical class I antigens, such as Qa2 glycoproteins, and their potential role in tumoregenicity. Methods Cloned cells from L1210 were treated with DTIC and then H-2D, and Qa antigen expression was studied on four clones, before and after xenogenization with DTIC. Results and conclusions a strong decrease of Qa2 molecule expression was demonstrated by radioimmunoassay and immunofluorescent staining and was confirmed by FACS and 2D-gel analysis. The presence or the absence of Qa antigens on tumor cells could thus be involved in tolerance or rejection of tumor cells in syngeneic animals.