title: Quantitation of L-selectin and CD18 expression on rabbit neutrophils during CD18-independent and CD18-dependent emigration in the lung.
abstract: In the systemic circulation, the leukocyte adhesion molecule, L-selectin facilitates the initial adhesion of the neutrophil to the inflamed endothelium, whereas CD11/CD18 is essential to transendothelial migration. Previous work from our laboratory showed that neutrophil emigration in the lung occurs through either a CD18-independent or CD18-dependent mechanism, depending on the inflammatory stimulus. This study quantitated and compared the surface expression of L-selectin and CD18 on neutrophils in the lungs of rabbits during emigration toward Streptococcus pneumoniae (a CD18-independent stimulus) and Escherichia coli endotoxin (a CD18-dependent stimulus). Ultrathin frozen lung tissue sections were immunogold labeled for 1-selectin and CD18, and gold particles were quantitated on intravascular, interstitial, and airspace neutrophils by transmission electron microscopy. The results show that CD18-independent neutrophil emigration was associated with L-selectin down-modulation (78%) and CD18 up-modulation (260%) on intravascular neutrophils, before emigration. A similar alteration in the expression of L-selectin and CD18 was observed during CD18-dependent neutrophil emigration, but only on neutrophils that emigrated into the interstitium and airspace. In emigration induced by either stimulus, alterations in L-selectin and CD18 expression were restricted to the inflammatory focus and emigrated airspace neutrophils consistently expressed greater levels of CD18 than intravascular and interstitial neutrophils. We conclude that before emigration, L-selectin and CD18 expression on intravascular neutrophils is altered only during CD18-independent emigration and only on those neutrophils within the inflammatory focus. The increased CD18 expression on airspace neutrophils may facilitate bacterial phagocytosis.
authors.affiliation: Pulmonary Research Laboratory, University of British Columbia, St. Paul's Hospital, Vancouver, Canada.
authors.forename: A R
authors.initials: AR
authors.lastname: Burns
authors.forename: C M
authors.initials: CM
authors.lastname: Doerschuk
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D018821:CD18 Antigens; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002634:Chemotaxis, Leukocyte; D004731:Endotoxins; D004926:Escherichia coli / Q000276:immunology; D005260:Female; D019041:L-Selectin; D008168:Lung / Q000166:cytology*; D009504:Neutrophils / Q000378:metabolism*; D011014:Pneumonia / Q000276:immunology*; D011817:Rabbits; D013296:Streptococcus pneumoniae / Q000276:immunology
chemical_list: D015703:Antigens, CD; D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D004731:Endotoxins; D019041:L-Selectin