Rajewsky, Harvard, Cambridge, MA; and SJL/J RAG2/mice by H. receptor, tolerance, ENMO == Abstract == Aquaporin-4 (AQP4)-specific T cells are expanded in neuromyelitis optica (NMO) patients and exhibit Th17 polarization. However , their pathogenic role in CNS autoimmune inflammatory disease is unclear. Although multiple AQP4 T-cell epitopes have been identified in WT C57BL/6 mice, we observed that neither immunization with all those determinants nor transfer of donor To cells focusing on them caused CNS autoimmune disease in recipient mice. In contrast, robust proliferation was seen following immunization of AQP4-deficient (AQP4/) mice with AQP4 peptide (p) 135153 or p201220, peptides predicted to contain I-Abrestricted T-cell epitopes but not determined in WT mice. In comparison with WT mice, AQP4/mice used unique T-cell receptor repertoires for acknowledgement of these two AQP4 epitopes. Donor To cells specific for either determinant coming from AQP4/, but not WT, mice induced paralysis in recipient WT and B-celldeficient mice. AQP4-specific Th17-polarized cells induced more severe disease than Th1-polarized cells. Clinical signs were associated with opticospinal BI-4924 infiltrates of T cells and monocytes. Fluorescent-labeled donor T cells were detected in CNS lesions. Visual system involvement was evident by changes in optical coherence tomography. Fine mapping of AQP4 p201220 and p135153 epitopes identified peptides within p201220 but not p135153, which induced clinical disease in 40% of WT mice by direct immunization. Our results provide a foundation to evaluate how AQP4-specific To cells contribute to AQP4-targeted CNS autoimmunity (ATCA) and suggest that pathogenic AQP4-specific T-cell responses are normally restrained by central tolerance, which may be relevant to understanding development of AQP4-reactive T cells in NMO. Neuromyelitis optica (NMO) is actually a rare, disabling, and sometimes fatal CNS autoimmune inflammatory demyelinating disease that causes attacks of paralysis and visual loss (1). Immunologic, epidemiologic, and pathologic proof suggests To cells come with an important role in the etiology of NMO (13). Pathogenic aquaporin-4 (AQP4)-specific antibodies in NMO serum are predominantly IgG1, a T-celldependent IgG subclass (4), and T-cellmediated CNS inflammation enables CNS access of those antibodies (5, 6). NMO susceptibility is associated with allelic MHC II genes, in particular HLA-DR17 (DRB1*0301) BI-4924 in some populations (7). AQP4-specific To cells have been identified in patients (8, 9), and T cells specific to get dominant AQP4 epitopes show Th17 polarization (8). It BI-4924 is therefore important to understand factors that control development and regulate the expression of AQP4-specific To cells in NMO. 1 cannot feasibly test whether AQP4-reactive To cells participate directly in CNS inflammation in NMO patients. Creature models can permit in vivo evaluation of the role of AQP4-specific T cells in CNS autoimmunity. Although multiple AQP4 T-cell epitopes have been determined in WT mice and rats (1013), attempts to create AQP4-targeted experimental BI-4924 NMO (ENMO) with clinical manifestations of CNS autoimmune disease by either direct immunization of those determinants or adoptive transfer of To cells focusing on them have been unsuccessful (1113). Recently, it was observed that immunization of AQP4-deficient (AQP4/) mice with AQP4 peptide (p) 135153 elicited T-cell proliferation and that those To cells induced mild clinical disease in 70% of recipient WT mice (14). Here, we evaluated T-cell reactivity to AQP4 in C57BL/6 AQP4/and WT mice and determined two pathogenic AQP4 T-cell determinants, 1 within AQP4 residues 135153 and one in 201220. Both determinants were predicted to bind MHC II (I-Ab) avidly and PIK3C2G elicit I-Abrestricted AQP4-specific CD4+T-cell responses (15), yet only T cells from AQP4/, but not WT, mice proliferated robustly to those epitopes. Hyperproliferation was AQP4-specific, as immunization with a myelin oligodendrocyte glycoprotein (MOG) peptide induced the same proliferation in AQP4/and WT mice. In contrast to T cells in WT mice, T-cell and T-cell receptor (TCR) repertoires used by AQP4-specific To cells in AQP4/mice were unique. Transfer of either AQP4 p135153- or p201220-specific Th17-polarized cells from AQP4/donor mice consistently induced paralysis and histologic CNS autoimmune disease in nearly 100% of nave recipient WT mice. Peptides within AQP4 201220 but not 135153 were BI-4924 determined that induced clinical disease in WT mice by direct immunization. AQP4-specific T-cellmediated clinical disease was associated with opticospinal infiltrates of To cells, W cells, and monocytes, and dynamic visual system.