Differences in polymorphonucleocyte function and local inflammatory response between horses and ponies.
BACKGROUND
Wound healing proceeds faster in ponies than in horses and complications during healing, such as wound infection, occur less frequently in ponies. Earlier studies suggested that this difference might be related to differences in the initial post traumatic inflammatory response.


OBJECTIVE
That polymorphonuclear leucocyte (PMN) function and profiles of humoral factors in local inflammatory processes are different in horses and ponies.


METHODS
PMNs were isolated from venous blood of horses and ponies. Chemotaxis and reactive oxygen species (ROS) production was determined. Tissue cages were implanted in limbs and necks of horses and ponies and injected with carrageenan and, 3 weeks later, with LPS. In sequential samples of inflammatory exudate, the numbers of macrophages and PMNs and the production of PGE2, TNFalpha, IL-1, IL-6 and chemoattractants were determined.


RESULTS
In vitro ROS production of PMNs was significantly higher in ponies than in horses, whereas in vitro PMN chemotaxis was significantly lower in ponies. In the tissue cages for both stimuli, the production of IL-1 and chemoattractants was significantly higher in ponies than in horses and remained so towards the end of the observation period in ponies.


CONCLUSIONS
This study demonstrated a higher production of various inflammatory mediators by pony leucocytes. Despite the lower in vitro chemotaxis of pony PMNs, this higher in vivo production resulted in a stronger initial inflammatory response in ponies, as has been reported in studies on wound healing, through the attraction of leucocytes and triggering of the production of other cytokines. A stronger initial inflammation may promote healing by more rapid elemination of contaminants and earlier transition to repair.


CONCLUSIONS
Modulation of the initial inflammatory response might therefore be a valid option for therapeutic intervention in cases of problematic wound healing. Further, the intraspecies differences in leucocyte function may have an impact on many fields in equine medicine.
D000818:Animals; D001947:Breeding; D002634:Chemotaxis, Leukocyte; D015194:Diffusion Chambers, Culture / Q000662:veterinary; D006734:Horse Diseases / Q000097:blood / Q000276:immunology* / Q000503:physiopathology; D006736:Horses / Q000293:injuries*; D007249:Inflammation / Q000276:immunology / Q000503:physiopathology / Q000662:veterinary*; D018836:Inflammation Mediators / Q000378:metabolism; D007958:Leukocyte Count / Q000662:veterinary; D008264:Macrophages / Q000166:cytology; D008297:Male; D009504:Neutrophils / Q000276:immunology / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013045:Species Specificity; D014945:Wound Healing / Q000502:physiology*; D014947:Wounds and Injuries / Q000662:veterinary
D018836:Inflammation Mediators; D017382:Reactive Oxygen Species