Our previous report showed that autoreactive IFN-γ+IL-10+CD4+ T cells can activate B cells to produce autoantibodies (165), and donor-type tissue-resident PD-1hiCD4+ T helper cells interact with B cells in the GVHD target tissues to produce autoantibodies that mediate thymus damage and cutaneous GVHD (166). The gene discussed is IL10; the disease is graft versus host disease.