Increased intestinal intra-epithelial T lymphocytes in primary glomerulonephritis: a role of oral tolerance breakdown in the pathophysiology of human primary glomerulonephritides?

BACKGROUND: There is increasing evidence that some organ-specific and generalized autoimmune diseases in humans might be related to a breakdown of oral tolerance. We explored this hypothesis in human primary glomerulonephritides. We prospectively counted intraepithelial T lymphocytes in the duodenal mucosa (as a marker of rupture of oral tolerance), together with IgA1 and IgA2 mucosal plasma cells, in patients with primary glomerulonephritides.
METHODS: We investigated eight adults with immune-complex glomerulopathy (membranous nephropathy+membranoproliferative glomerulonephritis), 16 adults with an idiopathic nephrotic syndrome, and 25 adults with IgA nephropathy. Patients with glomerulonephritides were compared to two control groups: group 1 consisted of nine healthy adults; group 2 comprised five adults with coeliac disease before dietary gluten withdrawal or during a clinical relapse related to gluten ingestion. (The latter disease is associated with increased numbers of intraepithelial T lymphocytes, and a breakdown of oral tolerance to gliadins is involved in the pathogenesis of coeliac disease). Duodenal fibroscopy was performed under neuroleptanalgesia. Four to six endoscopic biopsy specimens were taken from the second duodenum. Intraepithelial T lymphocytes were blindly counted on paraffin sections stained with haematein-eosin-saffron (HES), within the epithelium of a villus in a zone with at least 100 cells. Mucosal IgA1 and IgA2 plasma cells were blindly counted in a mucosal tissue unit by using specific mouse monoclonal antibodies directed against IgA1 and IgA2, with alkaline phosphatase anti-alkaline phosphatase (APAAP) revelation. As values were not normally distributed, we used non-parametric analysis of variance with the Kruskal-Wallis test, and compared median values by using the non-parametric Mann-Whitney test.
RESULTS: Intraepithelial T lymphocytes were significantly more abundant in patients with primary glomerulonephritides and coeliac disease than in healthy controls (P < 0.0001 in the Kruskal-Wallis test): healthy controls, median 11 (range 4.65-16); immune complex glomerulopathy, 27.45*** (15-93); idiopathic nephrotic syndrome, 16.5** (9-26.5); IgA nephropathy, 26.10*** (11.3-47.5); coeliac disease, 55*** (20-80) (*P <0.05; **P <0.01; ***P < 0.005, Mann-Whitney test). No difference was found in the number of duodenal IgA1 and IgA2 plasma cells between controls and patients with primary glomerulonephritides. IgA1 and IgA2 plasma cells were increased in patients with coeliac disease.
CONCLUSION: The significant increase in intestinal intraepithelial T lymphocytes in primary glomerulonephritides suggests a pathophysiological role of oral tolerance breakdown.