title: Mast cell-independent mechanisms of immediate hypersensitivity: a role for platelets.
abstract: Mast cells have been implicated as the central effectors in allergic responses, yet a fatal anaphylactic response can be induced in mast cell-deficient mice. In this study, we examined the immediate hypersensitivity response in wild-type (WT) and mast cell-deficient mice (W/W(v)) in two different tissues (skin and skeletal muscle). Vascular permeability and leukocyte recruitment were studied after immediate challenge or 4 h postchallenge in OVA-sensitized mice. In skin, immediate challenge induced a significant increase in vascular permeability (75%) within 30 min and was accompanied by increased leukocyte adhesion 4 h postchallenge. In the absence of mast cells, no changes in vascular permeability or leukocyte recruitment were observed in skin. In WT skeletal muscle, immediate challenge induced a rapid increase (80%) in vascular permeability within 5 min and significant leukocyte recruitment after 4 h. Surprisingly, in W/W(v), a gradual increase in vascular permeability was observed, reaching a maximum (50%) within 30 min. Despite the absence of mast cells, subsequent leukocyte emigration was similar to that observed in WT mice. Pretreatment with anti-platelet serum in W/W(v) returned Ag-induced vascular permeability and leukocyte recruitment to baseline. Platelets were shown to interact with endothelium in skeletal muscle, but not dermal microvasculature. These data illustrate that mast cells play a prominent role in vascular permeability and leukocyte recruitment in skin in response to Ag, however, in skeletal muscle; these changes can occur in the absence of mast cells, and are mediated, in part, by the presence of platelets.
authors.affiliation: Gastrointestinal Research Group, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Denise C
authors.initials: DC
authors.lastname: Cara
authors.forename: Kirsten V J
authors.initials: KV
authors.lastname: Ebbert
authors.forename: Donna-Marie
authors.initials: DM
authors.lastname: McCafferty
mesh_terms: D000485:Allergens / Q000008:administration & dosage; D000818:Animals; D001792:Blood Platelets / Q000276:immunology*; D002199:Capillary Permeability / Q000235:genetics / Q000276:immunology; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002450:Cell Communication / Q000235:genetics / Q000276:immunology; D002465:Cell Movement / Q000235:genetics / Q000276:immunology; D004727:Endothelium / Q000098:blood supply / Q000166:cytology / Q000276:immunology; D006969:Hypersensitivity, Immediate / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D007274:Injections, Intraperitoneal; D007962:Leukocytes / Q000166:cytology / Q000276:immunology; D008297:Male; D008407:Mast Cells / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D018482:Muscle, Skeletal / Q000098:blood supply / Q000276:immunology / Q000473:pathology; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000098:blood supply / Q000166:cytology / Q000276:immunology
chemical_list: D000485:Allergens; D010047:Ovalbumin