Age-dependent resistance of chickens to salmonella in vitro: phagocytic and bactericidal activities of splenic phagocytes.

The phagocytic and bactericidal activities to Salmonella pullorum (strain 9-25) or Salmonella senftenberg (strain 99D) were examined in chicken splenic phagocytes from 0-day-old to 2-month-old chickens. The phagocytic activity against S pullorum increased in splenic phagocytes from chickens older than 7 days, but significant changes in activity against S senftenberg were not observed during the experimental period. The bactericidal activity of splenic phagocytes against S senftenberg was higher than that of phagocytes against S pullorum during the same period. Increase of the bactericidal activity against S pullorum was observed with increasing age, but the activity of the splenic phagocytes from 0-day-old chickens against S senftenberg was similar to that of the phagocytes from 2-month-old chickens. Although delayed hypersensitivity was confirmed by delayed wattle reaction in 2-month-old chickens sensitized with living S pullorum, the sensitization did not markedly affect phagocytic and bactericidal activities.