Background: Uremia is associated to host defense mechanism disorders. Lymphocyte apoptosis, which may cause alteration of the immune system, is increased in uremic patients. The aim of the present study was to determine if, in addition to uremia, dialysis membranes with different biocompatibility and permeability have an effect on lymphocyte apoptosis.
Methods: Cell apoptosis and Fas expression were assessed using flow cytometry in four groups of patients: (1) uremic non-dialyzed (Non-D) patients; (2) hemodialysis (HD) patients on hemophan; (3) low-flux polysulfone, and (4) high-flux polysulfone membrane. Ten healthy volunteers were used as controls.
Results: At baseline, lymphocytes from patients on hemophan showed an increase in apoptosis (18.4 +/- 6.9%) as compared with Non-D (7.2 +/- 2.8%; p < 0.001), low-flux (6.4 +/- 2.4%; p < 0.001), high-flux (2.6 +/- 1.2%; p < 0.001) and controls (2.0 +/- 1.0%; p < 0.001). Fas expression was similar in lymphocytes from Non-D and hemophan dialyzed patients (40.5 +/- 5% vs. 40.4 +/- 6%), and in both groups it was greater than low-flux (30%+/-7%; p < 0.001), high-flux (11 +/- 4%; p < 0.001) and controls (12.6 +/- 3%; p < 0.001). When lymphocytes were cultured for 48 h, apoptosis was similar in Non-D and hemophan (27.0 +/- 4.3% vs. 27.1 +/- 6.9%); apoptosis of lymphocyte from patients on low-flux (14.1 +/- 3.5%) was greater than on high-flux polysulfone membrane (7.0 +/- 2.0%; p < 0.001).
Conclusion: These findings suggest that in dialysis patients lymphocyte apoptosis is influenced not only by the biocompatibility but also by the permeability of the dialysis membrane.