Importantly, elevated levels of plasma CXCL13 have also been shown to correlate with disease activity, and T cells appear to be the main producers of CXCL13 in the synovial tissue in patients with seropositive RA (Stephenson et al. 2018; Greisen et al. 2014), supporting the pathologic relevance of the Tph subset. The gene discussed is CXCL13; the disease is rheumatoid arthritis.