Moreover, in chronic HBV patients who spontaneously controlled the infection, i.e. patients who underwent HBsAg seroconversion without treatment, the frequency of global circulating PD-1+ CD4+ T cells was lower than in HBsAg+ patients, and the reduced expression of PD-1 was especially seen at the levels of Treg (152). The gene discussed is PDCD1; the disease is infection.