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 (Tregs), 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 CD3+, NKT lymphocyte subpopulations and Bcl2 expression on B cells was also observed in both groups. However, no changes were observed in the percentage of CD4+, CD8+, CD3+γδ+, CD19+, transitional B cells (CD24highCD38highCD19+CD27−), natural killer (NK), invariant NKT (iNKT) lymphocytes and Th1/Th2 balance when BT was compared with ET. At TT, IIT patients had a higher Tregs percentage than Co‐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 CD3+ percentage than Co‐H (P = 0·001) and a lower Bcl2 expression on B cells than Co‐H (P