INS and type 1 diabetes mellitus: In contrast to previous data showing a low level of insulin in glucagon+ cells of insulin-deficient islets of patients with longstanding T1D, in the present study, immunoreactivity to insulin was observed not only in glucagon+ cells of insulin-deficient islets, but also in the majority of glucagon+ cells of insulin-containing islets of children with recent-onset T1D and nondiabetic persons.