Mechanism of increased serum soluble interleukin-2 receptor levels in patients on continuous ambulatory peritoneal dialysis

Objective: The aim of this study was to investigate the mechanism underlying the increase of serum soluble interleukin-2 receptor (IL-2R) levels in patients on continuous ambulatory peritoneal dialysis. Material and Methods: In 13 dialysis patients and 17 healthy controls, serum soluble IL-2R levels were determined by enzyme-linked immunosorbent assay, and CD25-positive (cell surface IL-2R-positive) cells were detected by flow cytometry. Soluble IL-2R levels were also measured in the supernatant of cultured peripheral blood mononuclear cells. Results: The serum soluble IL-2R level was significantly higher in the patients than in the healthy controls (p < 0.0001). In contrast, both the percentage and the absolute count of CD25-positive cells showed no significant differences, and neither did the soluble IL-2R level in culture supernatant. Serum soluble IL-2R levels showed a positive correlation with the serum β₂-microglobulin level (p < 0.01), the age of the patients (p < 0.05), and duration of dialysis (p < 0.05), as well as a negative correlation with the urine volume (p < 0.05). Conclusions: The increase of serum soluble IL-2R in patients on peritoneal dialysis may be caused by accumulation due to its low transperitoneal clearance and low urinary excretion.