Expression of the LFA‐1 β2 Integrin (CD11a/CD18) and ICAM‐1 (CD54) in Normal and Coeliac Small Bowel Mucosa

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Abstract
The leucocyte adhesion molecules (β2 integrins) comprise CD11 α-chains and a common β-chain (CD18), CD11a (leucocyte Junction-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-Iweak 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 CD11a expression by IEL, seen predominantly in surface epithelium and mainly by the CD4+ minority subset, but not by CD4- CD8- (TcR γδ+) 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.