CD4 and autoimmune disease: Circulating Tfh (cTfh) cells, contain long-lived memory cells characterized by CD4+CXCR5+CD45RA- in peripheral blood, are functionally similar to GC Tfh cells, can induce autoantibody production by B cells, and play an important role in the pathogenesis of autoimmune diseases including SLE (19–23, 25, 26).