NOD mice with knockout of both native insulin genes and a mutated proinsulin transgene, alanine at position B16 in preproinsulin (B16:A-dKO mice), do not develop diabetes. Transplantation of NOD islets, but not bone marrow, expressing native insulin sequences (tyrosine at position B16) into B16:A-dKO mice rapidly restored development of insulin autoantibodies (IAAs) and insulitis, despite the recipients’ pancreatic islets lacking native insulin sequences. Splenocytes from B16:A-dKO mice that received native insulin–positive islets induced diabetes when transferred into wild-type NOD/SCID or B16:A-dKO NOD/SCID mice. Splenocytes from mice immunized with native insulin B chain amino acids 9–23 (insulin B:9–23) peptide in CFA induced rapid diabetes upon transfer only in recipients expressing the native insulin B:9–23 sequence in their pancreata. Additionally, CD4+ T cells from B16:A-dKO mice immunized with native insulin B:9–23 peptide promoted IAAs in NOD/SCID mice. These results indicate that the provision of native insulin B:9–23 sequences is sufficient to prime anti-insulin autoimmunity and that subsequent transfer of diabetes following peptide immunization requires native insulin B:9–23 expression in islets. Our findings demonstrate dependence on B16 alanine versus tyrosine of insulin B:9–23 for both the initial priming and the effector phase of NOD anti-islet autoimmunity.
Maki Nakayama, Joshua N. Beilke, Jean M. Jasinski, Masakazu Kobayashi, Dongmei Miao, Marcella Li, Marilyne G. Coulombe, Edwin Liu, John F. Elliott, Ronald G. Gill, George S. Eisenbarth
Bone marrow transplant with native B16:Y insulin genes is not sufficient to restore insulin autoimmunity.