A recent US cohort study identified that the activated circulating PD-1+ Tfh2 cells serve as a complementary biomarker of disease activity in the IgG4-related sclerosing pancreatitis and cholangitis in combination with other clinical markers, such as the plasmablasts and serum IgG4 and IgE, and as a potential target for immunotherapy based on decreases in the numbers of the PD1+ Tfh2-cell subsets after treatment, which is in line with clinical findings (103). The gene discussed is PDCD1; the disease is cholangitis.