The secondary aim was to compare plasma sIC levels between PeCa patients and cancer-free controls.<h4>Methods</h4>Using ProcartaPlex immunoassays, BTLA, IDO, LAG-3, HVEM, PD-1, PD-L1, PD-L2, TIM-3, CD80, CTLA-4, GITR, CD27, CD28, and CD137 were measured in plasma from 284 PeCa patients and 45 cancer-free controls. The gene discussed is IDO1; the disease is cancer.