β2-integrin/intercellular adhesion molecule (ICAM) expression in the normal human intestine.

The β2-integrin Family of adhesion molecules and their ligands. The ICAM molecules, probably have an important role to play in the intestinal immune response. To date, any data published regarding the intestinal expression or β2-integrins and ICAMs have mostly described only mucosal expression. The presence in the intestine of αd, a newly described β2-integrin molecule has not yet been determined. To understand further the expression of these molecules in all layers of the intestine, a comprehensive study was undertaken in both normal colon and normal small intestine specimens from 15 patients (colon n = 15. and ileum n = 6) who underwent surgical resections. Immunohistochemistry was performed for CD18, CD11a. CD11 b. CD11c. αd. ICAM-1, ICAM-2. and ICAM-3. The colon and small intestine cases were grouped separately and each of the mucosal, submucosal, muscle and adventitial layers were scored for expression. The β2-integrin molecules were expressed by mononuclear cells in all layers of the bowel, predominantly in the mucosa and adventitia. CD11a showed the greatest mucosal expression and CD11b showed the greatest adventitial expression, αd exhibited expression in all bowel layers, as well, with most intense expression in the mucosa and adventitia. CD11c exhibited the least expression of all α subunit molecules. The expression of these α-chains at times appeared to be greater than that seen for CD18 (β2), raising the possibility of non-β2-containing complexes (i.e. α-chains associating with an alternate β-chain). ICAM-l was expressed on endotheiium, particularly in the mucosa and rarely on mucosal mononuclear cells. ICAM-2 was predominantly on subtiuicosal endothelium and rarely expressed in colon mucosa and never expressed in ileal mucosa. ICAM-3 was expressed by mononuclear cells throughout the bowel wall, but also on adventitial endothelium in selected eases. In summary, we are reporting a comprehensive immunohistochemical study of the differential expression of β2-integrins, including the newly described αd molecule and the ICAM molecules in all layers of normal human colon and ileum. We raise the possibility that a second β2-integrin 3 subunit may exist, and we report that lCAM-3 is expressed on endothelium particularly in the adventitial layer. [ABSTRACT FROM AUTHOR]