Spatial distribution of cell adhesion molecules on the peritoneal surface in the cecal perforation-induced...

For understanding the immunological functions of the peritoneum, spatial localization of integrins and their ligands was studied by immuno-SEM on the peritoneal surface of mice with cecal perforation-induced peritonitis. The cecal peritoneum 24 hr after perforation was stained with specific antibodies against LFA-1, Mac-1, VLA-4, ICAM-1, VCAM-1, and fibronectin diluted with cold University of Wisconsin (UW) solution in conjunction with immuno-gold labeling. The spatial localization of those cell adhesion molecules was detected by backscatter electron (BSE) imaging with field emission scanning electron microscope (FESEM). Numerous leukocytes with diverse surface ultrastructure were observed on the peritoneal surface by FESEM. Some leukocytes were in contact with mesothelial cells, and others adhered to the exposed underlying connective tissue. The BSE imaging showed the ubiquitous distribution of Mac-1 on all membrane domains of leukocytes, i.e., cell body, ruffles, and microvilli. In contrast, predominant expressions of LFA-1 and VLA-4 were discernible on ruffles/microvilli of some leukocytes. The mesothelial cells remaining in the inflamed area expressed both ICAM-1 and VCAM-1 on their microvilli. The fibronectin was detected on presumable collagen fibers and/or fibrin over the exposed smooth muscle layer as well as on fibrin extending between leukocyte aggregation. The spatial microlocalization of integrins was clarified on the leukocytes emigrated in peritonitis, and their ligands were detected on the inflamed peritoneum.