LYMPHOCYTE SUBSETS IN DIALYZER ELUATES - A NEW PARAMETER OF BIOINCOMPATIBILITY

Introduction. During haemodialysis (HD), several adverse reactions in peripheral blood can occur, which have been attributed to the bioincom patibility of the dialyser membrane. Utilizing a dialyser elution tech nique, we have demonstrated that polymorphonuclear cells (PMN) manifes ted non-membrane dependent signs of activation during HD with cellulos e triacetate (CTA), cuprammonium (CU) and polysulphone (PS) membranes. In the present study, we employed this elution technique to investiga te the influence of HD with these membranes on lymphocytes. Methods. E ight patients were studied during HD with CTA, CU, and PS dialysers in a randomized crossover design. Dialyser elution was performed after 3 h of HD. Besides total leukocyte count and differentiation, lymphocyte subpopulations and activation status in peripheral blood and dialyser eluates were analysed by flow cytometry. Results. Only with CU was a significant leukocyte decrease observed in peripheral blood at 30 min (P<0.001). Neither the total number of lymphocytes nor the proportion of T(CD3+) and B(CD19+) cells had markedly changed after HD with eithe r membrane. Meanwhile, all membranes induced a relative decline in nat ural killer cells -NK(CD3-/CD16+/56+)- at the end of dialysis, althoug h this was only significant for CTA (P=0.04). As for T-lymphocyte subs ets, the proportion of CD4+ cells had markedly increased after three h ours of HD with all three dialysers, CTA and PS being significant (P<0 .05). Dialyser eluates contained 33.8-82.2 x 10(6) cells, CTA yielding the highest cell counts. The majority (81-91%) of the eluted cells co nsisted of PMN (dialyser eluates versus peripheral blood: P<0.05), whe reas only few lymphocytes were found (4-13%, absolute 2.6 x 10(6)). Ly mphocyte subpopulations in dialyser eluates were comparable to periphe ral blood at t 180 in case of CTA and CU. In contrast PS eluates conta ined significantly fewer T-cells (37%), but more B-cells (22%) and NK- cells (30%) in comparison with peripheral blood at 180 min (peripheral blood: 79, 6 and 16% respectively; P<0.05). The expression of activat ion markers on T-cells (HLA-DR, CD25) in dialyser eluates was comparab le with peripheral blood. Conclusion. The absolute number of lymphocyt es in dialyser eluates of CTA, CU, and PS dialysers was low (mean 2.6 x 10(6)) in comparison with peripheral blood (mean 1.4 x 10(9)/1). Whe reas non-selective adhesion occurred in CU and CTA dialysers, a select ive adhesion pattern of lymphocyte subpopulations was observed in case of PS, suggesting a difference in bioincompatibility. Apparent T-cell activation was not noted, either in peripheral blood or in dialyser e luates. Because PMN in the dialyser eluates of three different membran es showed similar activation patterns in a previous study, we hypothes ize that eluted lymphocytes, rather than PMN, represent a preferable p arameter of bioincompatibility.