Lymphocyte ectoenzymes in childhood idiopathic nephrotic syndrome

Lymphocyte ectoenzymes with immunomodulatory function were investigated in 11 children with minimal change disease (MCD), 9 with primary focal segmental glomerulosclerosis (FSGS), and 17 age- and sex-matched healthy children. Basal, concanavalin A (Con A)-, and pokeweed mitogen (PWM)-stimulated lymphocyte ecto-5′-nucleotidase (5′-Nu), dipeptidyl peptidase IV (DPP IV), and alkaline phosphodiesterase I (APD) activities were determined. In MCD relapse ecto-APD activity of unstimulated lymphocytes was higher than controls. Ecto-APD of Con A-stimulated lymphocytes was below controls (23.0, range 7.2– 48.7 nmol/min per 10⁶ lymphocytes) in all active MCD (18.7, range 7.6–32.6), during corticosteroid treatment (14.6, range 4.5–54), and in remission (13.1, range 6.1–19.6), but was significant only in remission. Con A-stimulated DPP IV was significantly lower from controls (53.8, range 19.3–85.7 nmol/min per 10⁶ lymphocytes) in all active MCD (38.1, range 10.8–82.1), during treatment (37.5, range 20.2–58.7), and in remission (39.4, range 24.3–69.6). In FSGS, unstimulated lymphocyte ecto-APD activity was greater than controls. However, Con A-stimulated lymphocyte ecto-APD and DPP IV activities were not significantly different from controls. Con A stimulation of lymphocyte ecto-APD and DPP IV activity was significantly reduced in MCD relapse and in remission, but not in FSGS. Basal, Con A-, and PWM-stimulated ecto-5′-Nu in MCD and FSGS were not different from controls. These results suggest a role for abnormal T cell function in MCD but not in FSGS. The difference in mitogen-stimulated expression of these ectoenzymes suggests a different pathogenesis of childhood MCD and primary FSGS. Received June 30, 1997; received in revised form May 13, 1998; accepted May 27, 1998