Impaired immunoglobulin G production in minimal change nephrotic syndrome in adults.

Serum IgG, T and B cell subsets, cytoplasmic IgG positive cells (cB gamma) and IgG in the medium (cIgG) of a 5 day culture of peripheral lymphocytes in both stimulated and non-stimulated (spontaneous) conditions with pokeweed mitogen (PWM) were studied in 30 adult patients with minimal change nephrotic syndrome (MCNS). In the nephrotic phase (11 patients), surface IgG positive B cells (sB gamma) and spontaneous cB gamma increased (P less than 0.05), whereas PWM-stimulated cIgG did not increase, and serum IgG decreased significantly (P less than 0.05). The cB gamma/sB gamma ratio calculated as an index of IgG synthesis in B cells increased spontaneously (P less than 0.05), but did not increase under PWM-stimulation. The cIgG/cB gamma ratio as an index of IgG secretion from each matured B cell, reduced in both spontaneous and stimulated conditions (P less than 0.05, P less than 0.01, respectively). In the phase of unstable remission maintained by steroid therapy (10 patients), these parameters tended to normalize and the OKT4/OKT8 ratio decreased (P less than 0.05), while the ratio remained unchanged in the nephrotic phase. However, after discontinuation of steroid (nine patients), spontaneous cB gamma and the spontaneous cB gamma/sB gamma ratio were again increased, and the cIgG/cB gamma ratio decreased (P less than 0.05) as observed in the nephrotic phase. These results suggest that B cells in patients with MCNS both in the nephrotic state and stable remission after discontinuation of steroid are activated spontaneously, but the secretory process of IgG from the matured cells is impaired, and that steroid improves these abnormalities.