Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves.

Introduction/aims: The precise relationship between molecular mimicry and tissue-specific autoimmunity is unknown. Major histocompatibility complex (MHC) class II antigen presenting cell-CD4+ T-cell receptor complex interactions are necessary for adaptive immunity. This study aimed to determine the role of endoneurial endothelial cell MHC class II in autoimmune polyneuropathy.

Methods: Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aa^flox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aa^flox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aa^flox/flox; vWF-iCre/+ mice to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in Tamoxifen-treated H2-Aa^flox/flox; vWF-iCre/+, H2-Aa^flox/flox; +/+, H2-Aa^+/+; vWF-iCre/+ and untreated H2-Aa^flox/flox; vWF-iCre/+ adult female SJL mice. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points.

Results: Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Tamoxifen-treated H2-Aa^flox/flox; vWF-iCre/+ mice were resistant to sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues.

Discussion: A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo was developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.