Recruitment of CXCR3+ T cells into injured tissues in adult IgA vasculitis patients correlates with disease activity

Objectives: Adult immunoglobulin A vasculitis (IgAV) is an immune complex small vessel vasculitis. So far, the involvement of T cells in this pathology has been poorly studied. The aim of this study was to analyze T-cell homeostasis as well as cytokine and chemokine concentrations in the blood and tissues of IgAV patients. Methods: T cells, cytokine and chemokine concentrations were analyzed in peripheral blood using flow cytometry and multiplex assays. T-cell infiltrates in the kidney and the skin were characterized by immunohistochemistry. This study prospectively included 44 adult patients with biopsy-proven IgAV and 24 age and sex-matched healthy controls. Results: We observed reduced proportions of circulating CXCR5-and CXCR3-expressing memory CD4 T cells at diagnosis but normal values at remission. The plasma levels of Th1-related cytokines (IL-12, IL-27 and IFN gamma) and of the TFH-related cytokine, IL-21, were paradoxically not reduced in patients. We observed increased plasma concentrations of the CXCR5 ligand, CXCL13, and of the CXCR3 ligands, CXCL10/11, suggesting a potential relocation of the corresponding T cells into inflamed tissues. We then confirmed the recruitment of CXCR3-expressing T cells into the skin and kidneys. In the skin, T-cell infiltrates mainly co-localized with damaged dermal small vessels. Finally, patients with the largest kidney T-cell infiltrates were also those with the highest proteinuria. Conclusion: Altogether, our results strongly suggest that, in IgAV patients, CXCL10/11 orchestrate the recruitment of CXCR3-expressing T cells in injured tissues, contributing to tissue damage and disease activity.