EFFECT OF LYMPHOCYTES FROM NEPHROTIC PATIENTS ON UPTAKE OF ³⁵S BY GLOMERULAR BASEMENT MEMBRANE

Abstract

Patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) have an increase in glomerular permeability to proteins due to the loss of fixed negative charges in the glomerular basement membrane (GBM). Heparan sulfate is the main compound carrying the anionic sites; SO₄ in this molecule represents an important source of the negative charges.

We have studied the effect of peripheral blood lymphocytes (PBL) from nephrotic patients on the incorporation of ³⁵S in rat GBM. ³⁵S uptake increased when glomeruli were incubated with lymphocytes from 10 patients with IMLNS in relapse compared to simultaneous assays on 5 controls (2295 ± 634 cpm/mg glomerular weight, mean ± SEM, and 962 ± 248 cpm/mg, respectively) (P<0.02).

³⁵S incorporation did not increase when glomeruli were incubated with PBL from seven patients with other glomerulopathies (1016 ± 503 cpm/mg) as compared to controls (1283 ± 642 cpm/mg) or from eight IMLNS patients in remission (822 ± 435 cpm/mg) as compared to controls (1475 ± 608 cpm/mg). No significant differences in ³⁵S uptake were seen between glomerular cultures with and without control PBL.

These data suggest a role for PBL in the pathogenesis of IMLNS, since the increased ³⁵S incorporation may be the result of increase catabolism of proteoglycans in the GBM. This may subsequently lead to decrease in anionic sites and increase in glomerular permeability.

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