Mononuclear phagocytes of transport-stressed horses with viral respiratory tract infection.

Twelve horses comprised 3 treatment groups; all horses in 2 of the groups had recently been transported and had clinical and laboratory evidence of respiratory tract infection, with equine influenza type 2 virus being the principal pathogen. Mononuclear phagocytes and other leukocytes from blood, lung, and peritoneal cavity were studied in phagocytosis and erythrocyte-antibody (EA) rosette assays. Total numbers of pulmonary alveolar macrophages were increased over control values in bronchoalveolar lavage (BAL) fluid of group 3 horses after recovery from influenza (P less than 0.02), whereas the increase in neutrophils in the fluid of those horses approached significance. Lymphocytes in BAL fluid of group 3 horses (after recovery from influenza) were in larger proportion than those in fluid of group 1 horses during acute influenza (P less than 0.05). Pulmonary alveolar macrophages of group 1 horses formed a lower percentage of EA rosettes than did those of controls (P less than 0.01) or group 3 horses (P less than 0.02). The differential counts of peritoneal macrophages and neutrophils in horses of groups 1 and 3 were virtually identical at the first collection, but differed from controls at the second collection 4 weeks later; peritoneal macrophages were reduced (P less than 0.01), whereas peritoneal neutrophils were increased (P less than 0.01). Peritoneal macrophages and peritoneal neutrophils of horses with acute influenza were phagocytic in larger proportion than were those in controls at both collection times (P less than 0.01 and P less than 0.01 for peritoneal macrophages, and P less than 0.01 and P less than 0.05 for peritoneal neutrophils, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)