OX40 Ligand Contributes to Human Lupus Pathogenesis by Promoting T Follicular Helper Response

Increased activity of T follicular helper (Tfh) cellsplays a major pathogenic role in systemic lupus ery-thematosus (SLE). However, the mechanisms thatcause aberrant Tfh cell responses in SLE remainelusive. Here we showed the OX40 ligand (OX40L)-OX40 axis contributes to the aberrant Tfh responsein SLE. OX40L was expressed by myeloid antigen-presenting cells (APCs), but not B cells, in bloodandininflamedtissuesinadultandpediatricSLEpa-tients. The frequency of circulating OX40L-express-ing myeloid APCs positively correlated with diseaseactivity and the frequency of ICOS