Submitted to: International Comparative Haematology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/26/2000
Publication Date: 2/1/2001
Citation: Interpretive Summary: Studies from our laboratory have shown that products (lymphokines) released by a type of white blood cell (the T lymphocyte) can stimulate a second type of white blood cell called the heterophil. Heterophils function by eating and destroying foreign objects, including bacteria like Salmonella, that invade the body of a baby chicken. The objective of this experiment was to test the ability of a specific type of lymphokine known as interferon-gamma to stimulate the eating and killing functions of heterophils from baby chickens. The results showed that the heterophils treated with interferon-gamma were able to eat and kill more bacteria than the heterophils that were not treated with interferon-gamma. These results are important because we now of know of a specific lymphokine that can stimulate one part of the baby chicken's immune system. This kind of treatment should make the baby chicken able to fight bacterial infections early in life.
Technical Abstract: Neonatal poultry exhibit a transient susceptibility to infectious diseases during the first week of life largely due to a qualitative impairment of the avian innate cellular defenses. Heterophils are critical phagocytic cells of the avian innate host defenses. Interferon-gamma (IFN-gamma) and a variety of other cytokines have been shown to augment the functional competence of neonatal mammalian neutrophils. The objective of the present studies was to examine the in vitro effects of recombinant chicken IFN- gamma (ChIFN-gamma) on shape change, phagocytosis, and the oxidative/nonoxidative killing activities of day-old chicken heterophils. Heterophils (4 x 10g/ml) were incubated with various concentrations of recombinant ChIFN-gamma from both E. coli and transfected COS cells for 2 h at 39 degrees C. The incubation of the neonatal heterophils with rChIFN- gamma resulted in significantly greater numbers of cells with membrane shape change when compared to the mock-treated heterophils. Both COS cell- derived and E.coli-derived ChIFN-gamma significantly increased (P < 0.01) the phagocytosis of opsonized or nonopsonized Salmonella enteritidis (SE) by the neonatal heterophils in a concentration-dependent manner. Incubation with ChIFN-gamma induced no direct stimulation of the respiratory burst, but did prime the heterophils for a significantly strengthened respiratory burst to subsequent stimulation with opsonized zymosan. Lastly, incubation of the heterophils with ChIFN-gamma primed the cells for a significant increase in the release of Beta-D glucuronidase following stimulation with opsonized zymosan. These results show that ChIFN-gamma can enhance the immune competence of the innate defenses of chickens during the first week of life.