Proteinase inhibitors in animal blood with special regard to equine pulmonary disease: ?1-proteinase inhibitor and ?2-macroglobulin

Abstract

Although the proteinase-proteinase inhibitor disequilibrium theory has been used to explain the development of lung disease in humans, it does not explain the high incidence of COPD in the horse. First, the genetic α1-PI deficiency shown in humans has never been observed in the horse and if such a disorder exists in the horse, it must be a very rare event which does not correlate with the COPD incidence. Second, since they are only present in low amounts, endogeneous elastolytic enzymes from neutrophils and macrophages in horses do not seem to play the fundamental role postulated by the disequilibrium theory of humans. Alternatively, exogeneous proteinases derived from fungi and bacteria, which are not neutralised by proteinase inhibitors in the blood, may be responsible for the generation of COPD in horses. Although α1-PI deficiency cannot be completely excluded as a cause of COPD, other proteinase inhibitors in the blood and body fluids may also be involved in this process.