Expression of MICA in the small bowel mucosa

ALLEGRETTI Y; BAYARDO M; RUMBO M; DRUT R; CUETO RUA E; ZWIRNER N; CHIRDO FG

Praga. Republica Checa

Congreso; 5th Meeting of the European Mucosal Immunology Group; 2006

European Mucosal Immunology Group

MIC (MHC class I chain related gene) A is expressed at low levels in normal intestinal epithelia, but is strongly induced in active coeliac disease (CD). The NKG2D receptor, expressed by intraepithelial lymphocytes (IEL), interacts with MICA and mediates cellular cytotoxicity of enterocytes. In this scenario, IL-15 appears as a key player since it induces MICA expression in enterocytes and cellular citotoxicity by IELs, among other effects. We investigated the expression of MICA in biopsy samples of the upper small bowel presenting different histological changes. The samples were collected from paediatric patients during the CD diagnostic protocol and grouped according to their histology. Immunohistochemistry analysis using a MICA-specific monoclonal antibody showed that in normal mucosa (n= 5) MICA is expressed at low levels. Eleven/15 samples with mild enteropathy and 6/8 samples with villous atrophy were MICA positive. MICA positive enterocytes were mainly recognized at the upper part of the villous. Confocal microscopy observation showed that staining in most of MICA positive enterocytes was intracellular at the supranuclear region. Severity of histological changes was in parallel with an increment in the number of MICA positive cells in the intraepithelial compartment as well as in round cells in lamina propria. In conclusion, MICA is upregulated in damaged intestinal mucosa. Positive staining was mainly observed in enterocytes on the top of the villi. Some IELs and round cells in the lamina propria, yet unidentified, also express MICA.