Interferon subverts an AHR-JUN axis to promote CXCL13 + T cells in lupus.

Systemic lupus erythematosus (SLE) is prototypical autoimmune disease driven by pathological T cell-B cell interactions 1,2 . Expansion of T follicular helper (T FH ) and T peripheral helper (T PH ) cells, two T cell populations that provide help to B cells, is a prominent feature of SLE 3,4 . Human T FH and T PH cells characteristically produce high levels of the B cell chemoattractant CXCL13 (refs.  5,6 ), yet regulation of T cell CXCL13 production and the relationship between CXCL13 + T cells and other T cell states remains unclear. Here, we identify an imbalance in CD4 + T cell phenotypes in patients with SLE, with expansion of PD-1 + /ICOS + CXCL13 + T cells and reduction of CD96 hi IL-22 + T cells. Using CRISPR screens, we identify the aryl hydrocarbon receptor (AHR) as a potent negative regulator of CXCL13 production by human CD4 + T cells. Transcriptomic, epigenetic and functional studies demonstrate that AHR coordinates with AP-1 family member JUN to prevent CXCL13 + T PH /T FH cell differentiation and promote an IL-22 + phenotype. Type I interferon, a pathogenic driver of SLE 7 , opposes AHR and JUN to promote T cell production of CXCL13. These results place CXCL13 + T PH /T FH cells on a polarization axis opposite from T helper 22 (T H 22) cells and reveal AHR, JUN and interferon as key regulators of these divergent T cell states.