DETECTION OF ABNORMAL PERIPHERAL-BLOOD MONONUCLEAR CELL CYTOKINE NETWORKS IN HUMAN-IGA NEPHROPATHY

Dysregulated cytokine expression has been implicated in the pathogeneis of IgA nephropathy, but the mechanisms and selectivity of this response are poorly understood. In this study we have examined the expression of a range of immunoregulatory cytokine mRNAs by peripheral blood mononuclear cells (PBMNCs) from 45 patients with IgA nephropathy stratified empirically according to urinary red cell excretion: 10 in remission, and 35 with active disease (21 mild, 14 moderate), and 17 normal, and 15 disease, controls. We used a semi-quantitative polymerase chain reaction (PCR) technique. None of the patients had experienced recent episodes of macroscopic hematuria. Simultaneous analysis of monocyte class II antigen (DR) expression was also performed by two-color immunoflow cytometry. TGF-beta1 mRNA was detected in 68% (24 of 35) of patients with active, and 70% (7 of 10) inactive IgA nephropathy, but in only 18% (3 of 17) normal (P < 0.005), and 27% (4 of 15) disease controls. IL-6 transcripts were identified in 37% (13 of 35) of patients with active IgA nephropathy, compared with 6% (1 of 17) normal controls (P = 0.015), with no significant increase in IgA remission, or disease control groups. TNF-alpha mRNA was detected in 29% (5 of 17) of normal and 53% (8 of 15) disease controls, but in only 7% (3 of 35) of patients with IgA nephropathy (P = 0.015). There was no significant change in TGF-beta2, gamma-IFN, IL-2, IL-4, IL-1alpha or IL-1beta detection between groups. There was an association between gamma-IFN and IL-6 mRNA detection in patients with active IgA nephropathy: 83% (5 of 6) with gamma-IFN transcripts also had detectable IL-6 mRNA, compared with 28% (8 of 29) of those without gamma-IFN transcripts (P = 0.01). There was also phenotypic evidence of cellular activation, with an increased percentage of monocytes expressing high levels of class II antigen in patients with moderately active nephropathy, mean (SD), 12.6 (4.8)%, compared with normal, 6.7 (1.6)% (P < 0.001), and disease controls, 7.5 (5.2)%. Furthermore, class II antigen expression was significantly higher in IgA nephropathy patients with detectable IL-6, 12.4 (5.1)%, and in particular, gamma-IFN mRNA, 14.3 (6.8)%, as opposed to those without detectable mRNA species, 8.8 (3.8)%, and 9.2 (3.7)%, respectively (P less-than-or-equal-to 0.02). These data suggest there is an abnormal interactive network of monocyte and T cell derived cytokines, associated with monocyte activation, in peripheral blood MNCs from patients with IgA nephropathy. This may have important implications for the pathogenesis of immune system abnormalities, renal cell injury and scar tissue formation in this disease.