EXPRESSION OF THE LFA-1 BETA-2 INTEGRIN (CD11A/CD18) AND ICAM-1 (CD54) IN NORMAL AND CELIAC SMALL-BOWEL MUCOSA

The leucocyte adhesion molecules (beta-2 integrins) comprise CD11 alpha-chains and a common beta-chain (CD18). CD11 a (leucocyte function-associated antigen 1, LFA-1) is expressed by most T cells, and is involved in antigen presentation by macrophages via its counter-receptor, intercellular adhesion molecule (ICAM-1, CD54). By criteria of double-label immunofluorescence of cryostat tissue sections, virtually all lamina propria T cells of the normal small bowel were found to express LFA-1 strongly. By contrast, only 30-60% of intra-epithelial lymphocytes (IEL) expressed detectable LFA-1, most of which were LFA-1weak and CD18-.ICAM-1 was expressed strongly only by vascular endothelium. In coeliac disease, there was a modest increase of diffuse ICAM-1 expression in the lamina propria, mainly in the subepithelial zone, where ICAM-1+ macrophages were occasionally seen. There was also a slight overall increase in CD11 a expression by IEL, seen predominantly in surface epithelium and mainly by the CD4+ minority subset, but not by CD4- CD8- (TcR gamma-delta+) cells. These data suggest that the LFA-1/ICAM-1-dependent antigen presentation pathway is of minor importance to IEL in the normal small bowel, and does not assume a major role in coeliac disease.