Continuous Ambulatory Peritoneal Dialysis Improves Immunodeficiency in Uremic Patients

F. Giacchino, MD, Nephrology and Dialysis Unit, San Giovanni Hospital, Largo Gottardo 143, I-10154 Turin (Italy) Dear Sir, The high incidence of infections and malignancies in uremic patients [1, 2] is a clear indication of the immuno-suppressive effect of uremia [3–5]. Numerous hypotheses have been put forward, including protein-calorie malnutrition [6], vitamin deficiency [7], and lowered blood zinc levels [8], but so far none of them has proved satisfactory. A more recent suggestion is that serum factors (medium molecular weight) may be responsible for this phenomenon in vitro [9], and in experimental animals [10]. There is still considerable debate however, as to whether middle molecules play a toxic role in cell-mediated immunity in man [11]. In order to evaluate the effect of different degrees of removal of middle molecules by dialysis treatment on cellular immunodeficiency, we analyzed the immunological state of 60 uremic patients treated by continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) during a follow-up of 12 months. 30 healthy people were also studied as controls. DNCB and PPD skin tests, Eand active Erosettes, the E-rosette inhibition assay were investigated as markers of cellular immunity [12]. The results of our study are summarized in table I. CAPD patients showed an improvement in cellular immunity, with a significant increase in the E-rosette count (p < O.Ol), and improved delayed hypersensitivity reactions 3 months after treatment was started, while no difference was observed in HD patients. The most compelling evidence for a role of middle molecules in cellmediated deficiency has been provided by the E-rosette inhibition test. Serum from CAPD patients showed a significant reduction of the percentage of E-rosette inhibition (p < 0.02), even 1 month after treatment was started, and the results were confirmed at the following controls. In the HD patients the percentage of inhibition remained high throughout our study. Our results are in agreement with previous findings in vitro and in animals [9, 10]. Since CAPD removes middle molecules more satisfactory than hemodialysis [13], and Table I. Cellular immunity in CAPD and HD patients