ICAM-1 expression patterns
During inflammation leukocytes are recruited from the blood into the infected regions. Recruitment is mainly dependent on the expression levels and distribution of adhesion molecules on the vessel wall. We are interested in ICAM-1,which is the major molecule mediating firm adhesion. To date most research of the inflammatory response has been focused on the aspects of venular circulation. Data from our laboratory indicates that arterioles also respond to inflammatory stimuli with an increased number of rolling leukocytes and increased solute permeability, suggesting that arterioles participate in the inflammatory response. The exact mechanisms involved and the differences between venular and arteriolar regulatory behavior are a focus of current work in our laboratory. The figures show ICAM-1 expression patterns among individual endothelial cells (ECs)imaged in blood perfused microvessels in anesthetized mice. We quantifiedICAM-1 immunofluorescence in adjacent pairs of ECs (shown by the black lines) by positioning the confocal plane on the top of the vessel where individual ECs could be observed (see the digital images at the top of the pictures). In venules under control and TNF-a activated conditions, ICAM-1 expression levels and distribution are similar in most of the sampled ECs (representative images and 3D surface intensityplots presented in panel A and B). In contrast, most arteriolar ECs expressed similar levels of ICAM-1 in adjacent cells under control conditions, but TNF- a treatment prduced much greater variability of ICAM-1 expression among ECs (representative images and 3D surface plots presented in panel C and D). We conclude from studies like this that arterioles express ICAM-1 very differently from venules, and we are currently studying the mechanisms underlying this difference.