Decreased Mucosal IgA level in the ileum of patients with chronic ulcerative colitis

ABSTRACT

Twenty patients [12 males and 8 females] with chronic ulcerative colitis with a mean [ +/- SEM] age of 32.6 +/- 2.2 y were Included in the study compared with twelve controls with noninflammatory conditions matching for age and sex. The diagnosis of chronic ulcerative colitis was established by colonoscopic appearance, histopathological study of biopsy specimens, and radiological examination. Colonoscopy was done and biopsy was taken from the ileum 10-15 cm from the ileo-caecal junction. A sandwich-type enzyme-linked immunoassay [ELISA] was used to measure the level of IgA in the supernatant of the homogenized samples. An immuno-histochemical study was performed on the fixed tissue specimens to count the number of IgA-positive mononuclear cells [MNC] /200 MNC in the lamina propria and their number in 10 high-power fields [HPF] [to calculate their concentration within the lamina propria]. There was no evidence of inflammation by light microscopy in any of the samples. The intensity of staining was decreased in biopsies taken from chronic ulcerative colitis patients compared with the controls. The mucosal IgA level was significantly lower in chronic ulcerative colitis patients compared with the control [7.22 +/- 0.84 and 12.34 +/- 1.86 mg/g total protein respectively, P < 0.05]. There was a statistically non-significant reduction in the number and concentration of IgA positive MNC in the patients compared with the controls [the number / 200 MNC was 54.72 +/- 6.94 for patients and 60.14 +/- 10.46 for controls, and the concentration /10 HPF was 213.2 +/- 56.6 for patients and 277.9 +/- 67.8 for controls]. There was no significant correlation between mucosal IgA level and the number of IgA positive MNC in 200 MNC or in 10 HPF. In conclusion, the level of mucosal IgA is reduced all through the gastro-intestinal tract in patients with chronic ulcerative colitis. This reduction is due to diminished production and /or secretion of IgA from the MNC. It is a primary change and it may be a factor in the development of chronic ulcerative colitis