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

The study investigates the effect of transport-stress and viral respiratory tract infection on the mononuclear phagocytes in horses. The findings suggest that horses recovering from equine influenza type 2 infection displayed more pulmonary alveolar macrophages and lymphocytes than horses in the acute stage of the disease, which might be crucial in the recovery process.

Design and Grouping

• The research involved twelve horses that were split into three groups: two of these groups consisted of horses that had recently been transported and showed signs of respiratory tract infection. The main virus found was equine influenza type 2.

Study Methodology and Techniques

• The researchers studied the mononuclear phagocytes (a type of white blood cell that helps fight off infections) obtained from the horse’s blood, lungs, and peritoneal cavity (the space within the abdomen that contains the intestines, stomach, and liver).
• They used phagocytosis (the process by which cells ingest harmful particles) and erythrocyte-antibody (EA) rosette assays (a laboratory technique to study cellular immune responses) to study these cells.

Findings

• The total count of pulmonary alveolar macrophages (a type of white blood cell in the lungs) went up in the bronchoalveolar lavage (BAL) fluid of the group 3 horses after they recovered from the influenza.
• Neutrophils (another type of white blood cell) in group 3 horses also increased, bordering on significance.
• The proportion of lymphocytes (also white blood cells) was higher in the BAL fluid of group 3 horses (post-recovery) compared to group 1 horses (during the acute phase of influenza).
• The phagocytes from the group 1 horses formed fewer EA rosettes than those from controls or group 3. This suggests compromised immunity during the acute phase of the disease.
• The counts of peritoneal macrophages and neutrophils in groups 1 and 3 were almost identical initially but deviated from controls four weeks later.
• At this point, peritoneal macrophages were reduced whereas peritoneal neutrophils had increased. The phagocytic activity of these cells was larger in the infected horses than in the controls.

Conclusion and Implications

• The findings suggest that horses recovering from influenza show an increase in certain types of white blood cells in their lungs, which might have implications in understanding the recovery process from the disease.