Production of interleukin-2 (IL-2) and expression of IL-2 receptor in patients with IgA nephropathy.

BACKGROUND

IL-2 production has been measured in several disease including type I diabetes mellitus, systemic lupus erythematosus, acquired immunodeficiency syndrome and active pulmonary sarcoidosis and its pathogenetic role was suggested. In IgA nephropathy, altered T cell subsets were reported to be associated with increased synthesis of IgA. The altered IL-2 production and the expression of IL-2 receptor might be involved in the pathogenesis of IgA nephropathy.

METHODS

To investigate the role of T cell mediated immunity in the pathogenesis of IgA nephropathy, the immune parameters such as T cell subsets, NK cell activity, interleukin-2 (IL-2) production and IL-2 receptor expression on peripheral blood mononuclear cells (PBMC) were measured before and/or after phytohemagglutinin (PHA) stimulation in 15 patients with IgA nephropathy. Age and sex matched 15 healthy controls and the correlations between the IL-2 production and immune parameters were evaluated.

RESULTS

The mean percentages of T helper/inducer cells (CD4), T suppressor/cytotoxic cells (CD8) and the CD4/CD8 ratio of the patients were not different from those of controls and the proportions of CD8 CD11b cell in the patients (21.0 +/- 3.6%) were significantly lower than those in controls (30.5 +/- 5.3%) (p < 0.005). The production of IL-2 by fresh PBMC of both patients and controls was in undetectable ranges. The production of IL-2 by PHA stimulated PBMC of patients was significantly higher than that of controls (140.03 +/- 43.2 U/ml vs 106.5 +/- 42.1 U/ml, p < 0.05). The proportions of lymphocytes expressing the IL-2 receptor (CD25) before the stimulation with PHA in patients were 1.22 +/- 1.00 percent and were not different from those in controls (1.12 +/- 0.78 percent). The correlations between the production of IL-2 and the concentrations of serum IgA, the degrees of histologic alterations and the proportions of CD8 and CD8CD11b cells were not significant. There was a weak tendency of a positive correlation (p < 0.1) between the production of IL-2 and the proportions of CD4 cells, and the CD4/CD8 ratio showed a significant correlation with the production of IL-2 (p < 0.05). After PHA stimulation, the mean percentages of lymphocytes expressing the IL-2 receptors in patients were increased to 47.6 +/- 8.9 percents which is higher than those (40.4 +/- 9.9%) in controls (p < 0.05). The NK cell activity of the patients was higher than that of controls (75.6 +/- 19.6% vs 56.1 +/- 16.2%, p < 0.005), and was well correlated with the production of IL-2 by PBMC (r = 0.89, p < 0.05).

CONCLUSIONS

It seemed that patients with IgA nephropathy have an 'latent' cellular immunoregulatory dysfunction that becomes apparent on the stimulation of extrinsic antigens or mitogens.