Longevity of augmented phagocytic activity of heterophils in neonatal chickens following administration of Salmonella enteritidis-immune lymphokines to chickens.

Previously, our laboratory reported an existing relationship between ontogenesis of heterophil activity and susceptibility to Salmonella enteritidis infection in poultry during the first week post-hatch. The prophylactic administration of S. enteritidis-immune lymphokines has been shown to enhance heterophil function in vitro and reduce S. enteritidis organ invasion in 1-day-old chicks. However, how long the heterophils remain activated is currently unknown. The objective of this research was to evaluate the duration of enhanced heterophil phagocytosis of S. enteritidis following the prophylactic administration of a single injection of S. enteritidis-immune lymphokines to neonatal chicks. Administration of S. enteritidis-immune lymphokines on the day of hatch resulted in a significant increase in heterophil phagocytic activity (P < 0.05) through day 5 post-hatch. No significant differences in phagocytic activities of heterophils from control and S. enteritidis-immune lymphokinetreated chicks was demonstrated from day 6 to 14 post-hatch. These data suggest that the administration of S. enteritidis-immune lymphokines on day of hatch potentiates heterophil phagocytic activity during a critical period of susceptibility to Salmonella infection in neonatal chicks. The immune lymphokine-induced enhancement of heterophil activity subsides by day 5 as the chick's natural defenses mature and are able to resist infections without exogenous augmentation.