|Ferro, Pamela - TX A&M UNIVERSITY|
|Rothwell, Lisa - INST FOR ANIMAL HEALTH|
|Kaiser, Pete - INST FOR ANIMAL HEALTH|
Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 2004
Publication Date: February 1, 2005
Citation: Ferro, P.J., Swaggerty, C.L., He, H., Rothwell, L., Kaiser, P., Kogut, M.H. 2005. Recombinant chicken IL-6 does not activate heterophils isloated from day-old chickens in vitro. Developmental and Comparative Immunology. 29:375-383. Interpretive Summary: The immune system of a baby chick during the first week of life is not very good at fighting infections. There are cells in the blood of baby chicks that help fight infections called heterophils. Our lab has shown that heterophils produce cell related chemicals called cytokines in response to different stimulants, such as Salmonella. Others have shown that other cells also produce similar cytokines in response to infection with Salmonella. One of these cytokines is IL-6. The purpose of the current study was to determine if IL-6 would have an effect on isolated heterophils in vitro (outside of the chick). We found IL-6 to have no direct effect on isolated heterophils. Identifying cytokines that are capable of stimulating cells of the immune system would be beneficial in the search for alternatives to antibiotic usage in food animals.
Technical Abstract: In all species so far studied, pro-inflammatory cytokines are produced as part of the innate immune response to bacterial invasion. In vitro, the invasion of chicken epithelial cells by Salmonella enteritidis (SE) induced an eight- to tenfold increase in the production of the pro-inflammatory cytokine IL-6. Additionally, an increase in heterophil pro-inflammatory cytokine gene expression, particularly IL-8 and IL-6, was associated with decreased susceptibility to extraintestinal SE infection in young broiler chickens. Taken together with the fact that invasion by SE induces an influx of heterophils to the site of infection, we speculated that heterophils would be responsive to IL-6 by both local chemotaxis and functional activation. Therefore, the objective of the present study was to determine if COS cell-derived recombinant chicken interleukin 6 (rChIL-6) would have an effect on the in vitro functional activity of heterophils isolated from day-old leghorn chickens. Isolated heterophils were incubated with various concentrations of rChIL-6 or mock-transfected COS cell supernatant for 2 hours at 39 deg C. Heterophil functional activity was assessed using five different functional assays measuring chemotaxis, phagocytosis, bactericidal activity, oxidative burst, and degranulation. Heterophils treated with rChIL-6 showed no functional differences, neither upregulation nor activation, compared to either untreated heterophils or heterophils treated with COS supernatants. These data indicate rChIL-6, alone, does not prime or activate avian heterophils. Therefore, the function of IL-6 in the local environment in response to SE invasion is still unknown.