MIGRATORY RESPONSES OF OVINE NEUTROPHILS TO INFLAMMATORY MEDIATORS INVITRO AND INVIVO

The migration of In-111-labeled ovine neutrophils toward a range of inflammatory mediators was examined in vitro using a 48-well chemotaxis chamber. Typical curves were obtained for the chemotactic response to zymosan-activated plasma (ZAP, a source of C5a) and interleukin-8 (1L-8). In contrast, leukotriene B4 (LTB4), platelet-activating factor (PAF), interleukin-1alpha (IL-1alpha), tumor necrosis factor alpha (TNF-alpha), N-formyl-methionine-leucyl-phenylalanine (fMLP), and endotoxins from Escherichia coli and Pseudomonas aeruginosa failed to induce neutrophil migration in vitro. Of these mediators LTB4, ZAP, IL-1alpha, TNF-alpha, IFN-gamma, and IL-8 have been reported to induce neutrophil accumulation in skin of sheep [1], and in the current study E. coli endotoxin was a potent inducer of In-111-labeled neutrophil accumulation and plasma leakage in skin. In contrast, PAF induced intense plasma leakage but failed to induce accumulation of In-111-labeled neutrophils in skin. Histologic examination of skin sites receiving PAF confirmed the failure of PAF to stimulate neutrophil extravasation. FMLP lacked inflammatory activity in skin. Coinjection of actinomycin D did not abrogate recruitment of neutrophils to skin sites receiving LTB4; thus neither induction of endothelial adhesion molecules nor synthesis of IL-8 was necessary for LTB4 to exhibit inflammatory activity in vivo.