Local expression of B7-H1 promotes organ-specific autoimmunity and transplant rejection

Abstract

moter [RIP].B7-H1) that expressed B7-H1 on pancreatic islet β cells.Unexpectedly, the transplantation of B7-H1-expressing islets resulted in accelerated allograft rejection in a B7-H1-dependent manner.Furthermore, a significant fraction of RIP.B7-H1 mice developed T cell-dependent spontaneous autoimmune diabetes.Finally, ectopic B7-H1 expression enhanced T cell priming and promoted autoimmunity induction in a T cell adoptive transfer model of diabetes.Thus, this study has revealed that tissue-specific expression of B7-H1 can costimulate T cell-mediated responses in vivo, resulting in accelerated allograft rejection, the breakdown of immune tolerance, and autoimmune disease pathogenesis. Methods Mice.RIP-membrane ovalbumin (RIP.mOVA) and OT-I transgenic mice have been previously described (21) and were generous gifts from William Heath (The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia) and Susan Webb (The Scripps Research Institute, La Jolla, California, USA).C57BL/6 and 129 mice were purchased from The Jackson Laboratory (Bar Harbor, Maine, USA).The mice were maintained under specific pathogen-free conditions.Animal care and use were in accordance with institutional and National Institutes of Health (NIH) guidelines. Generation of the transgenic mice.Full-length murine B7-H1 complementary deoxyribonucleic acid (cDNA) was synthesized by RT-PCR of splenic total RNA, and cloned into pCDNA3.1 (Invitrogen Corp., Carlsbad, California, USA) to produce the pCDNA3.1/B7-H1construct.The construct was generated by insertion of the fulllength murine B7-H1 cDNA into the ClaI site of RIP7 at position +180.A 10.6-kb fragment was excised by double digestion with NotI/SalI and was used for microinjection by the University of Chicago Cancer Research Center Transgenic Mice Facility.BamHIdigested tail DNA from mice was hybridized to a radiolabeled fulllength murine B7-H1-specific probe.Two positive founders were generated directly on a C57BL/6 background with an approximate copy number of seven, as determined by phosphorimager analysis Local expression of B7-H1 promotes organ-specific autoimmunity and transplant rejection