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Recurrent airway obstruction (RAO), also known as heaves, is an allergic respiratory condition that develops in horses following an exposure to aeroallergens in hay and straw. This is manifested by airway hyperreactivity, inflammation, bronchoconstriction, as well as a leukocyte and platelet infiltration into the airways. Platelet activation and an increase in circulating platelet-leukocyte aggregates may lead to airway remodeling. The aim of this study was to explore the effect of seven-day antigen challenge on dynamics of platelet indices and CD41/61 and CD62 P expression on platelets in horses with RAO. Ten RAO-affected horses and ten healthy horses were included in this study. All horses were exposed to 7 days hay and straw challenge. Blood samples were collected prior to the challenge (Pre-challenge) and 1, 2, 3, 7 and 14 days after the initiating the antigen challenge. Blood samples were obtained to determine the platelet count (PLT), mean platelet volume (MPV) and platelet large cell ratio (P-LCR). Expression of CD62 P and CD41/61 was detected by flow cytometry on activated platelets. Antigen challenge resulted in a significant gradual decrease of PLT in RAO horses, but not in controls. MPV and P-LCR in control and RAO-affected horses remained unchanged after antigen challenge. The expression of CD62 P and CD41/61 in RAO horses was significantly higher compared to control horses. The antigen challenge resulted in an increase expression of CD62 P and CD41/61 on the platelets of RAO-affected horses, while did not lead to significant changes in the control group. An increased expression of CD62 P and CD41/61 indicates platelet activation what may contribute to the formation of platelet aggregates in their respiratory system. [ABSTRACT FROM AUTHOR]

Recurrent airway obstruction (RAO) is an allergic disease of horses similar to human asthma, which is characterized by airway inflammation and activation of neutrophils, lymphocytes and platelets. Platelet activation and an increase in circulating platelet-leukocyte aggregates may lead to airway remodeling. The aim of this study was to investigate platelet status in RAO-affected horses based on the platelet morphology and platelet surface expression of CD41/61 and CD62P. Ten RAO-affected horses and ten healthy horses were included in this study. Blood samples were obtained to determine the platelet count (PLT), mean platelet volume (MPV) and platelet large cell ratio (P-LCR). Expression of CD62P and CD41/61 was detected by flow cytometry on activated platelets. The median PLT was significantly reduced in horses with RAO compared to the controls. The MPV and the P-LCR values were significantly higher in RAO horses than controls. Expression of CD41/61 on platelets was increased in RAO horses, while CD62P expression was reduced. This study demonstrated the morphological changes in platelets and expression of platelet surface receptors. Despite the decrease of CD62P expression, the observed increased surface expression of CD41/61 on platelets in horses with RAO may contribute to the formation of platelet aggregates in their respiratory system. [ABSTRACT FROM AUTHOR]