The role of plasma coating on the permeation of cytokine-inducing substances through dialyser membranes

We studied the effects of coating of dialyser membranes with plasma proteins on the permeation of bacteria-derived cytokine-inducing substances (CIS). An in vitro dialysis circuit using polysulphone (PS) or modified cellulose triacetate (mCT) dialysers was used. Precoating of the dialysers was performed by recirculation of 10% normal human plasma for 30 min in the blood compartment and subsequent rinse with pyrogen-free saline. Samples from the blood compartment were tested for induction of interleukin-1α (IL-1α), interleukin-1β (IL-1β) and tumour necrosis factor (TNFα) at various time points after challenging the dialysate with sterile culture supernatants from Pseudomonas aeruginosa. Contamination of the dialysate resulted in the appearance of CIS in the blood compartment of both polysuphone modified cellulose triacetate (IL-1α: PS, time 0: 81±11 pg/ml, time 60 min: 4747±1822 pg/ml, P<0.05; mCT, time 0: 235±141 pg/ml, time 60 min: 1632±531 pg/ml, P<0.05). The plasma protein layer reduced the penetration of CIS significantly only for polysulphone (IL-1α: PS, time 60: 4747±1822 versus 880±525 pg/ml, P<0.05; modified cellulose triacetate, time 60 min: 1632±531 pg/ml versus 930±326 pg/ml). Samples from the blood compartment contained <6 pg/ml LAL-reactive material at all time points. We conclude that plasma coating of polysulphone dialysers reduces the permeability for CIS derived from Pseudomonas, either by reducing the effective pore size or by adsorption of proteins that bind CIS. When precoated dialysers were used, transfer of CIS through both dialysers was comparable, suggesting that under the conditions of in vivo haemodialysis there may be no difference between the dialysers regarding the penetration of CIS from the dialysate