EFFECT OF PLASMA-PROTEIN ADSORPTION ON PROTEIN EXCRETION IN KIDNEY-TRANSPLANT RECIPIENTS WITH RECURRENT NEPHROTIC SYNDROME

Background. Among patients with the idiopathic nephrotic syndrome who have focal and segmental glomerulosclerosis and undergo renal transpla ntation, 15 to 55 percent have recurrent nephrotic syndrome. The recur rence may be caused by a plasma factor or factors that increase glomer ular permeability, because plasma exchange transiently decreases or ab olishes proteinuria in some patients. We studied the effect on protein uria of the removal of protein (mostly immunoglobulins) by adsorption onto protein A from the plasma of patients with recurrent nephrotic sy ndrome. Methods. Eight patients were treated with one to three cycles of two to seven 1-day sessions of protein adsorption, and the patients ' urinary protein excretion was measured repeatedly. Their immunosuppr essive regimens were not changed during the treatment. The adsorbed pr oteins were eluted from the protein A and injected into rats, and the urinary albumin excretion of the rats was measured. Results. The prote in-adsorption treatment consistently decreased urinary protein excreti on by an average of 82 percent at the end of a cycle (P<0.001). In one patient proteinuria disappeared, and in another urinary protein excre tion remained below 2.5 g per day with repeated cycles of protein adso rption. In all but one patient the effect of adsorption was limited in time, with a return to the preadsorption level of protein excretion w ithin a maximum of two months. The administration to rats of material eluted from the protein A increased urinary albumin excretion 2.9- to 4.6-fold (P<0.001 and P = 0.005, respectively). Although protein A pri marily binds immunoglobulins, the active fraction of the eluted protei ns had a molecular weight below 100,000, indicating that immunoglobuli n was not directly involved. Conclusions. Adsorption of plasma protein decreases urinary protein excretion in patients with recurrence of th e nephrotic syndrome after renal transplantation. Studies of the adsor bed proteins should provide information about the mechanism of this di sease.