Stress diminishes infiltration and oxygen metabolism of phagocytic cells in calves

The influences of a stress situation on the phagocytic cell function before and after infection with Pasteurella haemolytica were measured in calves. No differences in phagocytic and metabolic activity of alveolar macrophages (AMs) were observed in vitro between cells isolated from stressed and nonstressed animals. The uptake of bacteria and the migration of polymorphonuclear leukocytes (PMNs) did not differ. However, the production of superoxide by PMNs isolated from stressed animals was significantly diminished as compared to control PMNs. The stressed and six of the nine control calves were then infected intrabronchially with P. haemolytica. Phagocytic cell function was again evaluated after three days. The lavage fluid obtained from the lungs of the infected animals contained about three times more PMNs and six times more AMs as compared to the lavage fluid of the control calves. However, the increase in phagocytic cell numbers was less by half in the calves infected after the stress period. No differences were detected in phagocytic and metabolic activity of PMNs and AMs among control, infected, and stressed and infected calves. However, the chemotactic activities of PMNs obtained from infected stressed and infected nonstressed animals were diminished as compared to control PMNs. In conclusion, the metabolic responsiveness of PMNs is diminished and the accumulation of phagocytic cells at a site of infection is reduced after a stress period.