Increased Indoleamine 2,3-Dioxygenase in Monocytes of Patients on Hemodialysis

Hemodialysis patients suffer from susceptibility to infections. Inflammation upregulates indoleamine 2,3-dioxygenase (IDO) in the antigen-presenting cells, which suppresses T-cell function. Plasma IDO activity or protein expression is increased in hemodialysis patients and is associated with immune disturbances. This observation, however, does not consider many factors, importantly the source of IDO, which has to be the antigen-presenting cells in order IDO to exert its immunosuppressive effect in the microenvironment of the immune response. In this study, monocytes were isolated from 30 hemodialysis patients and 20 healthy volunteers and IDO was assessed by Western blotting. The IDO level in the monocytes of hemodialysis patients was significantly, almost 3-fold, higher than in the monocytes of healthy volunteers. This localization enables IDO to exert its immunosuppressive effect and supports conclusions of previous studies that used more indirect methods for assessing the role of this enzyme in the context of the immune response in hemodialysis patients.