Plasma Indoleamine 2,3-Dioxygenase and Arginase Type I May Contribute to Decreased Blood T-Cell Count in Hemodialysis Patients

Background: Acquired immunity is impaired in hemodialysis (HD) patients, and decreased T-cell number may contribute. Indoleamine 2,3-dioxygenase (IDO) and arginase type I (ARG) catabolize tryptophane and arginine, respectively, and exert proapoptotic and antiproliferative effects on T-cells. Plasma levels of IDO and ARG and their relation to blood T-cell number were evaluated in HD patients. Methods: Thirty-two HD patients and 20 healthy controls participated in the study. Plasma IDO and ARG were measured by means of enzyme-linked immunosorbent assay. T-cell number was assessed by means of flow cytometry. Results: IDO concentration was significantly higher in HD patients than in healthy volunteers (44.30 +/- 31.83 ng/mL vs. 21.28 +/- 26.21 ng/mL, p = 0.009). There was a trend for higher ARG concentration in HD patients (13.43 +/- 11.91 ng/mL) than in healthy volunteers (9.56 +/- 4.03 ng/mL), which, however, did not reach statistic significance (p = 0.099). Absolute T-cell count was significantly lower in HD patients than in healthy controls (1176.99 +/- 567.71 cells/mm(3) vs. 1519.85 +/- 594.96 cells/mm(3), p = 0.040). Absolute blood T-cell number was inversely related to plasma IDO (r = -0.490, p = 0.004) and to plasma ARG (r = -0.387, p = 0.029) concentrations. Conclusions: Plasma IDO and ARG may contribute to decreased blood T-cell count in HD patients.