title: Mechanisms of decreased leukocyte localization in the developing host.
abstract: Delays in leukocyte localization likely contribute to diminished host defense in neonates. Understanding the processes that may be affected has been hampered by the lack of suitable developmental models. Using intravital microscopy, we directly examine leukocyte recruitment in a rabbit pup model. In response to intraperitoneal interleukin (IL)-1beta, there were one-third as many leukocytes that arrested in pup mesenteric vessels and emigrated compared with adult vessels, although leukocyte flux was not different. Leukocyte rolling velocity in pups was one-half that in adults. In response to surgical trauma alone, the number of arrested pup cells was 15% that of adult cells, although again leukocyte flux was not different. An anti-L-selectin antibody inhibited rolling significantly by 60 min for both pups and adults. The effect on arrest and emigration occurred at significantly earlier times, although the effect was less in rabbit pups. A primary defect in leukocyte emigration in the rabbit pup appears to be a failure of the cell to transition efficiently from rolling to arrest. L-selectin-dependent adhesion and emigration are decreased, rolling is not, suggesting that at least part of the defect is due to events downstream of the initial tether.
authors.affiliation: Department of Pediatrics, Sections of Leukocyte Biology and Critical Care Medicine, Baylor College of Medicine, Houston, Texas 77030-2600, USA. marym@bcm.tmc.edu
authors.forename: M Michele
authors.initials: MM
authors.lastname: Mariscalco
authors.forename: Wilfredo
authors.initials: W
authors.lastname: Vergara
authors.forename: Jia
authors.initials: J
authors.lastname: Mei
authors.forename: E O'Brian
authors.initials: EO
authors.lastname: Smith
authors.forename: C Wayne
authors.initials: CW
authors.lastname: Smith
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn / Q000276:immunology*; D000906:Antibodies / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology; D062109:Dermatologic Surgical Procedures; D007375:Interleukin-1 / Q000494:pharmacology; D019041:L-Selectin / Q000276:immunology; D007962:Leukocytes / Q000166:cytology* / Q000276:immunology*; D008853:Microscopy / Q000379:methods; D011817:Rabbits; D012867:Skin / Q000276:immunology / Q000293:injuries; D013152:Splanchnic Circulation
chemical_list: D000906:Antibodies; D007375:Interleukin-1; D019041:L-Selectin