IFN-γ priming of chicken heterophils upregulates the expression of proinflammatory and Thl cytokine mRNA following receptor-mediated phagocytosis of Salmonella enterica serovar enteritidis

Responsiveness to invasive pathogens, clearance via the inflammatory response, and activation of appropriate acquired responses are all coordinated by innate host defenses. Polymorphonuclear leukocytes (PMNs) are cellular components of innate response, with the primary PMN in poultry being the heterophil. Priming is the potentiation of the phagocyte activation process. Interferon-γ (IFN-γ) is a pleiotropic cytokine involved in basically all phases of immune and inflammatory responses that has been shown to prime heterophil functional activities. In the present experiments, using real-time quantitative RT-PCR, we evaluated the role of recombinant chicken IFN-γ (rChIFN-γ) as a priming mediator to control heterophil responses at the level of gene transcription and expression of the mRNA for proinflammatory (interleukin-1β [IL-1β], IL-6, IL-8) and Th1 (IL-18 and IFN-γ) cytokine genes following stimulation with phagocytosis agonists, opsonized and nonopsonized Salmonella enteritidis. rChIFN-γ primed the heterophils for an increase in transcription of proinflammatory cytokines induced by phagocytic agonists but also upregulated expression of Th1 cytokine (IL-18 and IFN-γ) mRNA and stimulated an increased production of IFN-γ. Although rChIFN-γ priming modulated the expression of cytokine mRNA in heterophils stimulated by different phagocytic agonists, rChIFN-γ by itself did not directly induce gene expression of either proinflammatory or Th1 cytokines. The enhanced expression of cytokine mRNA does not appear to be differentially expressed depending on the receptor activated during phagocytosis. The results from the present experiments suggest that rChIFN-γ may play a significant role in avian innate immunity against Salmonella infection and may offer an adjunct use in the prevention and treatment of salmonellae infections in newly hatched chickens.