Previously we reported disease-specific interaction between interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in patients with IgA nephropathy (IgAN), suggesting the existence of unusual T cell behavior in this disease. In the present study, we investigated characteristic synthesis of interferon-gamma (IFN-gamma) and expression of IFN-gamma receptor (IFN-gamma R) in the peripheral blood mononuclear cells (PBMC) from patients with IgAN and other chronic proliferative glomerulonephritis (PGN). Heparinized peripheral blood samples were obtained from 38 patients with chronic mesangial proliferative glomerulonephritis (CGN; including 24 with IgA nephropathy) and 20 healthy controls. PBMC were isolated by gradient centrifugation and fragments were cultured in Iscove's modified Dulbecco's medium (IMDM) supplemented with 10% fetal calf serum (FCS) for 72 hr. IFN-gamma concentrations in supernatants were evaluated by the enzyme-linked immunosorbent assay (ELISA). Other parts of PBMC pellets were reacted with anti-human IFN-gamma R monoclonal antibody and FITC-labeled anti-mouse second antibody for analysis of IFN-gamma R expression on these cells by FACScan. The remaining PBMC were fractionated into CD4+ T cells, CD8+ T cells, B cells, NK, cells and macrophages using the MACS cell sorting system. The isolated cells were evaluated for IFN-gamma or IFN-gamma R mRNA expression by the semiquantitative RT-PCR method. In vitro IFN-gamma synthesis was enhanced in patients with CGN, and NK cells were revealed to be responsible for such enhancement. On the other hand, the expression of IFN-gamma R on macrophages was suppressed in CGN patients. These results suggest that impairment of regulation of the IFN-gamma system might be involved in the development of CGN.

To determine the cytokines responsible for the increase in production of IgA in patients with IgA nephropathy (IgAN), the roles of interleukin-4 (IL-4) and soluble CD23 (sCD23) were examined. Peripheral blood mononuclear cells (PBMCs) and serum were obtained from 24 patients with IgAN and 14 patients with non-IgA proliferative glomerulonephritis. Twenty healthy adults served as controls. Concentrations of IgA and IgE in 10-day culture supernatants of PBMCs were measured by the sandwich ELISA method. Levels of sCD23 and activities of IL-4 in 4-day (96-hour) culture supernatants and serum were measured by ELISA and bioassay, respectively. Activities of IL-4 both in culture supernatants and serum were significantly elevated in patients with IgAN compared with controls (1.26 ± 0.53 vs. 0.68 ± 0.37 U/ml in culture supernatants, p < 0.05; 1.35 ± 1.34 vs. 0.89 ± 0.82 U/ml in serum, p < 0.05). Levels of sCD23 in IgAN patients’ serum were also significantly elevated (521.7 ± 514.9 vs. 173.0 ± 166.2 U/ml, p < 0.01). In vitro IgA and IgE synthesis were suppressed by anti-IL-4 monoclonal antibody (mAb) only when the antibody was added on the day when the culture was started (day 0). No suppression of IgA or IgE synthesis was observed when the antibody was added on day 4. IgE but not IgA synthesis was suppressed by anti-CD23 mAb when added on both days 0 and 4. Serum levels of IgE showed positive correlations with serum activities of IL-4 and with levels of serum sCD23. It is concluded that IL-4 and sCD23 might play decisive roles in in vitro and in vivo hyperproduction of IgA and IgE in patients with IgAN, and that sCD23 seemed to control IgE but not IgA synthesis through a unique pathway.

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