Chicken macrophages, when treated with inducible nitric oxide synthase (iNOS) short interfering RNA (siRNA) and then stimulated with recombinant chicken IFN-γ, produced significantly less nitric oxide (NO) and had lower iNOS mRNA levels compared to IFN-γ stimulated HD-11 cells not treated with siRNA.

As gene knock-outs are not readily available for most agricultural species, such as the chicken, siRNA technology to reduce gene expression could prove to be a powerful tool in advancing basic knowledge of avian immune function and immune response to infection. Our novel demonstration of siRNA-mediated knock-down of iNOS mRNA expression and NO production in HD-11 macrophages establishes the validity and feasibility of using RNAi technology in the avian immune system, thus providing a foundation for future investigations in avian immune function and the chicken immune response to bacterial pathogens of economic importance such as Salmonella enteritidis.