T cells are responsive to the simian virus 40 large tumor antigen transgenically expressed in pancreatic islets

The qualities of a peripheral Ag that determine whether T cells will be tolerant of or responsive to it are poorly understood. To approach this problem, we studied the T cell response in a line of transgenic mice selectively expressing an oncoprotein in the islets of Langerhans. The SV40 large tumor Ag (SV40-T) is directed to islet beta-cells in Rip1-Tag3 (RT3) mice by a hybrid insulin promoter-SV40-T construct. Ag is first detected on these cells between 10 and 12 wk after birth. RT3 mice were bred with mice expressing a transgenic rearranged TCR recognizing SV40-T in the context of the class I MHC molecule, H-2Kk. T cell response in the resultant RT3/TCR-double transgenic mice was then analyzed. T cells are fully responsive to SV40-T in RT3/TCR-transgenic mice, and T cells infiltrate the islets of both RT3 and RT3/TCR-transgenic mice. This work demonstrates that T cells may remain responsive to self-Ag expressed outside the thymus, and that this responsiveness may result in autoimmunity. The developmentally delayed expression or the oncogenic nature of SV40-T in the RT3-transgenic mice may be important in determining this T cell response.