Further, PD1+CXCR5-CD4+ T cells were present at a high frequency in the IgH[MOG] CNS parenchyma and dura mater; these cells resembled T peripheral helper (Tph) cells, a recently described effector T cell subset that associates with B cells in the inflamed synovium in rheumatoid arthritis (RA)27. This evidence concerns the gene CXCR5 and rheumatoid arthritis.