Abnormal T lymphocyte function and reduced
interleukin-2 (IL-2) production have been implicated in the pathogenesis of the
nephrotic syndrome (NS). We investigated: (1) lymphocyte subpopulations and expression of
IL-2 receptor (IL-2R) on T cells using two-colour flow cytometry, (2) serum
IL-2 and (3) the soluble component of IL-2R (sIL-2R) in serum, using
enzyme-linked
immunosorbent assay, in 38 children with NS. All children, except those in remission, had marked
proteinuria. They were divided into groups according to renal pathology: (1)
steroid-sensitive NS (SSNS) not receiving
prednisolone therapy, (2) SSNS on
prednisolone, (3)
focal segmental glomerulosclerosis (FSGS), (4) SSNS in remission and not receiving
prednisolone therapy, (5) congenital NS (CNS). Results were compared with 26 age-matched controls. Total T lymphocytes (CD3) were reduced in groups 1 and 2; CD4 count was reduced in groups 1-4; CD8 count increased in groups 2 and 3; CD8 and CD19 (B lymphocytes) were significantly reduced in group 5. Increased IL-2R expression (CD25) on CD4 lymphocytes was noted in groups 1, 2 and 3 implying activation of these cells. In patients with SSNS, increased serum sIL-2R was recorded during relapse (1,273 +/- 497 U/l vs. 913 +/- 401 U/l in remission, P < 0.005) but free serum
IL-2 was not detectable at any stage. The specific alterations in lymphocyte subpopulations in SSNS and FSGS would imply an involvement of the immune system distinct from that in CNS.