Expression of the VLA family of integrins in human intestine

The distribution of cells expressing the integrins VLA-1 to 6 in human intestine was examined by alkaline phosphatase immunohistochemistry using monoclonal antibodies specific for the individual alpha-chains of the VLA heterodimer. VLA-2,3, and 6 were expressed on all epithelial cells in the small and large bowel. VLA-1 was expressed on crypt cells in the small and large bowel, but was only weakly expressed or was absent on villus epithelial cells in the small bowel and colonic surface epithelial cells. All epithelia were negative for VLA-4 and VLA-5. Intraepithelial lymphocytes were VLA-1+ and VLA-4+. VLA-1,3, and 5 were expressed uniformly by muscularis propria, muscularis mucosae, pericrypt cells, and smooth muscle fibres within the villi. By contrast, VLA-2 and 4 were present only in pericrypt cells and fibres within the villi; they were absent from the muscularis mucosae. VLA-1,3,5, and 6 were expressed by endothelium. Staining of muscle fibres and endothelium in the lamina propria made it difficult to determine the extent of VLA expression on lamina propria lymphocytes. However, VLA-1+ cells with lymphoid morphology were only rarely seen. All mononuclear cells in the lamina propria were VLA-4+.