Similarly, expanding CD4+ICOS+CD38+ and CD8+ICOS+CD38+ T-cell populations share features of pathogenic Tph cells that were previously described in the synovium of rheumatoid arthritis patients that were CXCR5−PD1+BCL6lo and retained a potent ability to promote B-cell differentiation35. This evidence concerns the gene TPH1 and rheumatoid arthritis.