Beta 2-integrin/intercellular adhesion molecule (ICAM) expression in the normal human intestine

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Beta 2-integrins and ICAMs are crucial for intestinal immune responses.
• Previous studies focused mainly on mucosal expression, neglecting deeper layers.
• The expression of the alpha d beta 2-integrin subunit in the intestine was unknown.

Purpose of the Study:

• To comprehensively analyze the expression of beta 2-integrins and ICAMs across all layers of the normal human colon and ileum.
• To determine the expression pattern of the alpha d beta 2-integrin subunit.
• To investigate potential non-beta 2-containing complexes involving alpha-chains.

Main Methods:

• Immunohistochemistry was performed on normal colon and ileum specimens from 15 patients.
• Expression of CD18, CD11a, CD11b, CD11c, alpha d, ICAM-1, ICAM-2, and ICAM-3 was assessed in mucosal, submucosal, muscle, and adventitial layers.
• Expression levels were scored separately for colon and small intestine tissues.

Main Results:

• Beta 2-integrins were present in mononuclear cells throughout all bowel layers, with highest expression in mucosa and adventitia.
• Alpha d was expressed in all layers, predominantly in the mucosa and adventitia. CD11a and CD11b showed distinct layer-specific expression.
• ICAM-1, ICAM-2, and ICAM-3 exhibited differential expression on endothelial cells and mononuclear cells across various intestinal layers.

Conclusions:

• Beta 2-integrins, including alpha d, are widely expressed in all layers of the normal human intestine.
• The expression patterns suggest a role for these molecules in the intestinal immune system beyond the mucosa.
• Findings raise the possibility of alternative beta-chain associations with alpha-chains and highlight ICAM-3's presence on adventitial endothelium.