In recent years, the role of immune checkpoints in the treatment of cancer was increasingly recognized, but unfortunately, little attention was paid to the significant role they played both in the development of secondary diabetes with immune checkpoint inhibitors and the treatment of T1D, such as cytotoxic T-lymphocyte antigen 4(CTLA-4), programmed cell death protein-1(PD-1), lymphocyte activation gene-3(LAG3), programmed death ligand-1(PD-L1), and T-cell immunoglobulin mucin protein-3(TIM-3). The gene discussed is HAVCR2; the disease is diabetes mellitus.