In addition to FDCs, recent studies have identified pathogenic CD4+PD-1highCXCR5- T cells, named peripheral helper T (Tph) cells, as CXCL13-producing cells in autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE)9–11. The gene discussed is CD4; the disease is rheumatoid arthritis.