Expression of P-glycoprotein in lymphocytes from children with nephrotic syndrome, depending on their steroid response

The aim of this study was to examine the expression of P-glycoprotein (P-gp) in CD3 lymphocytes of children with nephrotic syndrome (NS) in relation to their clinical response to glucocorticoid (GC) treatment. The examinations were performed on two groups. The study group (I) consisted of 88 children aged 2.0–20.0 years with NS, divided according to their clinical response to GC: NFR—non-frequent relapse NS; FR—frequent relapse NS; SD—steroid-dependent NS. The control group (II) consisted of 18 healthy children never treated with GC. We measured P-gp expression on CD3 lymphocytes of patients with NS using a flow cytometry assay. The CD3/P-gp was significantly higher than in controls. The difference was higher in SD (P=0.0001) and FR - (P=0.0002) group. The difference in NFR was smaller. Mean CD3/P-gp (in percent) was twice as high in SD children than in NFR, and the difference, as between FR and NFR, was statistically significant (P<0.01). Worse response to GC or dependency may be due to overexpression of P-gp. Further examinations are necessary to establish whether increased P-gp activity is a result of MDR-1 polymorphism and to determine GC response, or to ascertain if such activity is only a result of GC therapy.