Neuropilin-1 (NRP1) expression distinguishes self-reactive helper T cells in systemic autoimmune disease.

Pathogenic T helper cells (Th cells) that respond to self-antigen cannot be easily distinguished from beneficial Th cells. These cells can generate systemic autoimmune disease in response to widely expressed self-antigens. In this study, we have identified neuropilin-1 (NRP1) as a cell surface marker of self-reactive Th cells. NRP1 Th cells, absent in non-regulatory T cell subsets in normal mice, appeared in models of systemic autoimmune disease and strongly correlated with disease symptoms. NRP1 Th cells were greatly reduced in Nr4a2 cKO mice, which have reduced self-reactive responses but showed normal responses against exogenous antigens. Transfer of NRP1 Th cells was sufficient to initiate or accelerate systemic autoimmune disease, and targeting NRP1-expressing Th cells therapeutically ameliorated SLE-like autoimmune symptoms in BXSB-Yaa mice. Peripheral NRP1 Th cells were significantly increased in human SLE patients. Our data suggest that self-reactive Th cells can be phenotypically distinguished within the Th cell pool. These findings offer a novel approach to identify self-reactive Th cells and target them to treat systemic autoimmune disease.