Inflammatory neuropathy driven by a pathologically expanded, clonal lineage of IL-21 producing CD4+ T cells [TCR-seq]
CIDP (chronic inflammatory demyelinating polyneuropathy) is a debilitating immune-mediated neuropathy characterized by progressive weakness and sensory loss. Peripheral nerves from affected patients and mouse models show infiltrating CD4+ T cells, and CD4+ T cells from affected mice are sufficient to transfer neuropathy to immunodeficient recipients, suggesting an important role for CD4+ T cells in disease pathogenesis. Yet, key properties of pathogenic CD4+ T cells remain incompletely understood. Here, we report that IL-21 expression is highly expressed and a unique feature of terminally-differentiated effector CD4+ T cells within peripheral nerves of neuropathic mice. IL-21-expressing CD4+ T cells are comprised of two transcriptionally distinct, clonally expanded populations, which express genes associated with Tfh and Tph subsets.  Remarkably, TCR clonotypes were shared between these two IL-21-expressing populations, suggesting lineage differentiation from a common progenitor. Finally, we demonstrate that IL-21 signaling is required for pathogenic T cell infiltration into peripheral nerves through upregulation of CXCR6, a chemokine receptor that promotes CD4+ T cell localization in peripheral nerves. Together, these findings highlight IL-21 signaling, Tfh and Tph differentiation, and CXCR6-mediated cellular localization as key pathogenic pathways and potential therapeutic targets in inflammatory neuropathies. Overall design: This dataset contains single cell TCR-seq data from sciatic nerve-infiltrating CD45+ cells isolated from 4 neuropathic NOD.AireGW/+ mice