~Division of Pulmonary Medicine

Abstract--Inasmuch as the recruitment of polymorphonuclear leukocytes (PMNs) to inflammatory foci in vivo involves adhesion-dependent vents (e~g., margination, diapedesis, and directed migration), we sought to characterize the relationship between the local accumulation of PMNs in sterile peritonitis and their surface expression of the adhesion-promoting plasma membrane glycopmtein, Mol (CD1 lb/ CD18). In an immunofluorescence analysis of PMNs isolated from rats injected intraperitoneally with sterile 1 % glycogen solution, we detected a significant enhancement of surface Mol expression by exudative peritoneal PMNs. In contrast, no significant rise in Mol expression was noted over time by circulating intravas-cular PMNs (isolated simultaneously). However, these intravascular PMNs had the capacity to increase their surface Mol density upon exposure to peritoneal fluid supernatant a 37 ~ These results demonstrate hat PMNs at sites of inflammation in vivo do up-modulate their surface expression of the adhesion-promoting Mol glycoprotein during their recruitment from the circulating, intravascular leukocyte pool