“In vitro” effects of recombinant human interleukin 8 (rh-IL8) on chemotaxis of neutrophils: Differences between sheep and cattle

"IN VITRO" EFFECTS OF RECOMBINANT HUMAN INTERLEUKIN 8 (rh-IL8) ON CHEMOTAXIS OF NEUTROPHILS: DIFFERENCES BETWEEN SHEEP AND CATTLE. Comazzi S., Paltrinieri S., Sartorelli P., Istituto di Patologia Generale Veterinaria, via Celoria 10, Milan, Italy. Many infectious diseases in ruminants involve alterations in neutrophil (PMN) functions. In previous works we studied different steps of sheep neutrophil phagocytosis in basal conditions and after stimulation, in presence of pathological concentration of ketone bodies1 or in stress conditions2. "In vitro" investigation of chemotaxis is particularly interesting in some acute diseases that lead to PMNs' diapedesis and extravasation (abscesses, mastitis, rumenitis, etc). In human and in dog recombinant-human Interleukin-8 (rh-IL8) is a good activator of neutrophils chemotaxis. In this work "in vitro" neutrophils chemotaxis in sheep and in cattle was compared in basal conditions and after stimulation with omologous zymosan-activated serum (ZAS) and with rh-IL8. PMN were isolated as described by Carlson and Kaneko3 from blood samples from cattle and sheep. Chemotaxis assays were performed in a modified Boyden chamber and the distance run by the cells in a cellulose nitrate filter in basal condition (chemokinesis) and after stimulation with ZAS (50%) and of rh-IL8 (25 ng/ml) were evaluated by the leading front method. Ovine neutrophils showed higher levels of chemokinesis than those from cattle (p<0.001). ZAS stimulation greatly increased chemotaxis both in sheep and in cattle (p<0.05) while rh-IL8 activated chemotaxis only in ovine neutrophils (p<0.05). Rh-IL8 strongly activates neutrophil chemotaxis in many species. In cattle, concentrations of 75 ng/ml of rh-IL8 are reported to activate greater neonatal PMNs' transendothelial migration compared to adults4. The leading front method at our concentration has not been reported. The difference in response to ZAS and rh-IL8 is probably related to the different receptor involved in activation and our results suggest a lower expression of IL8-receptors in cattle than in sheep and indicate the use of ZAS as a good stimulator for the bovine neutrophils chemotaxis assay. The use of recombinant bovine interleukin-8 or of a higher concentration of rh-IL8 could better explain the role of this cytokine in inducing bovine neutrophils chemotaxis. References: 1 – Paltrinieri S, Sartorelli P, Agnes F. (1996) Eur. J. Haematol. 57 (Suppl. 59):18 2 – Sartorelli P, Paltrinieri S. (1993) Atti S.I.S.Vet, 47:1105 3 – Carlson GP, Kaneko JJ. (1973) Proc. Soc. Exp. Biol. Med. 142:853 4 – Bochsler PN, Neilsen NR, Slauson DO (1994) J. Leukocyte Biol. 53:273