Effect of dialysis on serum/plasma levels of free immunoglobulin light chains in end-stage renal disease patients

Background. Free immunoglobulin light chains (FLCs) have previously been shown to be uraemic toxins. In this work we investigated the effect of haemodialysis and haemodiafiltration on the level of FLCs in serum/plasma of uraemic patients. Methods. Serum/plasma proteins were separated by non-reducing SDS PAGE and transferred to a nitrocellulose membrane. FLCs were detected by specific antibodies and an enhanced chemiluminescence detection system. The FLC concentrations were calculated. We studied 15 healthy subjects, 10 patients with chronic renal failure, 71 patients undergoing haemodialysis treatment and 33 patients treated with haemodiafiltration. Different membranes were compared: low- and high-flux polysulfone membranes, low- and high-flux cellulose triacetate membranes, high-flux polymethylmethacrylate and polyacrylonitrile membranes. Results. Chronic renal failure patients showed elevated FLC concentrations as compared with controls. In haemodialysis or haemodiafiltration patients these values were even higher. This was mainly due to an increased concentration of FLC of the lambda-type. The treatment modality per se did not influence the FLC concentrations. Only haemodialysis or haemodiafiltration with the polymethylmethacrylate membrane lead to a significant reduction in FLC concentrations; however, these did not reach control levels. We did not observe differences in FLC levels between patients with different underlying diseases, nor did we find a correlation between age or the duration of the dialysis treatment and FLC concentrations. We found a positive correlation between FLC concentrations at the beginning of dialysis treatment and the amount of IgLCs removed during treatment. However, the average FLC level after treatment did not reach control values. Conclusions. Currently available haemodialysis or haemodiafiltration treatments are unable to normalize the elevated serum/plasma levels of FLCs in end-stage renal disease patients.