Heterogeneity of antigen expression explains controversy over glomerular macrophage accumulation in mouse glomerulonephritis

SUMMARY: Interleukin-10 (IL-10) has been recognized as a growth factor for rat mesangial cells in vitro ; however, its role in mesangioproliferative glomerulonephritis is unknown. We studied the expression of IL-10 mRNA in the rat anti-Thy-1 model of mesangioproliferative glomerulonephritis (experiment 1) and, subsequently, the effects of blocking IL-10 during anti-Thy-1 nephritis using the IL-10 inhibitor, AS101 (experiment 2). In experiment 1, PCR analysis failed to detect IL-10 mRNA in normal rat kidney, however, a clear signal for IL-10 mRNA was evident on day 6 of anti-Thy-1 nephritis. In situ hybridization showed IL-10 mRNA expression in focal glomerular areas in anti-Thy-1 nephritis. Combined in situ hybridization and immunohistochemistry showed that glomerular IL-10 mRNA was expressed by both macrophages and mesangial cells. In experiment 2, treatment with AS101 significantly downregulated renal IL-10 gene expression, as demonstrated by semiquantitative PCR. However, the induction of glomerular hypercellularity, mesangial proliferation (PCNA + cells), mesangial cell activation ( I? -SMA expression) and macrophage accumulation (ED1 + cells) seen in saline-treated anti- Thy-1 nephritis was unaffected by AS101 treatment. In conclusion, renal IL-10 gene expression is upregulated during pathological mesangial cell proliferation in rats with anti-Thy-1 nephritis. However, the inability of IL-10 suppression with AS101 to prevent anti-Thy-1 disease suggests that IL-10 is not essential for pathological mesangial cell proliferation.