Immunosuppressive activity of serum lipoproteins from patients with idiopathic nephrotic syndrome

Serum from patients with idiopathic minimal-change nephrotic syndrome (INS) inhibited concanavalin A (Con A) - induced lymphocyte proliferative response and rosette formation of lymphocytes with sheep erythrocytes (E). The inhibitory effect on Con A response was observed in not only INS serum but also in hyperlipidemic serum from some glomerulonephritis and hyperlipoproteinemia and was related to the serum lipid level. However, the inhibitory effect on E rosette formation was more specific for INS and was not related to the serum lipid level. Low density lipoprotein (LDL) from INS serum was more effective than that from normal serum in the inhibition of Con A response. On E rosette formation, only LDL from INS serum had inhibitory activity. Lipoprotein depleted serum did not inhibit either Con A response or E rosette formation. From these results, we speculated that LDL of INS serum contains some specific immunosuppressive factors different from those in normal LDL.