They showed that in patients with untreated IgG4-RD compared with those with primary Sjögren’s syndrome, those with multi-centric Castleman’s disease, and HCs, the number of circulating Tfh2 cells (defined as CD3+CD4+CD45RA−CXCR5+CXCR3−CCR6−) was significantly increased. The gene discussed is CD4; the disease is immunoglobulin G4-related sclerosing disease.