IDO1 and cervical carcinoma: CTLA-4 is believed to inhibit T-cell proliferation by blunting the antigen presenting cells thus providing negative feedback in the immune response (12, 18).Other immune checkpoints being studied in cervical cancer include indoleamine 2,3-dioxygenase 1 (IDO1), lymphocyte-activation gene 3 (LAG3), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3), glucocorticoid-induced TNFR-related protein (GITR), and T cell immunoreceptor with Ig and ITIM domains (TIGHT).