Regulatory T cells and other lymphocyte subpopulations in patients with melanoma developing interferon‐induced thyroiditis during high‐dose interferon‐α2b treatment

Summary Context One of the side effects of interferon‐alpha therapy is interferon‐induced thyroiditis ( IIT ). The role of lymphocyte subpopulations in IIT melanoma patients remains to be defined. Objective Our objective was to assess different peripheral blood lymphocyte subpopulations, mainly regulatory T cells ( T regs), in melanoma patients who developed IIT . Design, patients and methods From 30 melanoma patients receiving high‐dose interferon ( HDI )‐alpha 2b ( IFN ‐α2b) treatment, those who developed IIT ( IIT patients) were selected and compared with patients who did not develop IIT (Co‐ MM ) and healthy controls (Co‐ H ). Peripheral blood mononuclear cells were obtained before treatment ( BT ), mid‐treatment ( MT ), end of treatment ( ET ), 24 weeks post‐treatment and at appearance of IIT ( TT ). Results Nine patients developed IIT (30%): four Hashimoto's thyroiditis and five destructive thyroiditis. An increase in Tregs was observed in both melanoma groups during HDI treatment. A decrease in CD 3 + , NKT lymphocyte subpopulations and B cl2 expression on B cells was also observed in both groups. However, no changes were observed in the percentage of CD 4 + , CD 8 + , CD 3 + γδ + , CD 19 + , transitional B cells ( CD 24 high CD 38 high CD 19 + CD 27 − ), natural killer ( NK ), invariant NKT ( iNKT ) lymphocytes and T h1/ T h2 balance when BT was compared with ET . At TT , IIT patients had a higher T regs percentage than C o‐ MM ( P  = 0·012) and Co‐ H ( P  = 0·004), a higher iNKT percentage than Co‐ MM ( P  = 0·011), a higher transitional B cells percentage than Co‐ H ( P  = 0·015), a lower CD 3 + percentage than Co‐ H ( P  = 0·001) and a lower B cl2 expression on B cells than Co‐ H ( P  < 0·001). Conclusions Our results point to the immunomodulatory effects of IFN ‐α on different lymphocyte subpopulations and a possible role of T regs in melanoma patients who developed IIT .