Directional responses following recombinant cytokine stimulation of rainbow trout (Oncorhynchus mykiss) RTS-II macrophage cells as revealed by transcriptome profiling

Background: The early stages of the immune response are regulated by key cytokines including both interleukin 1 beta ( IL- 1 beta) and interferon-gamma ( IFN-gamma) which stimulate panels of responsive genes via conserved signal transduction pathways. To further our understanding of the transcriptional response to these cytokines in lower vertebrates we have utilized microarray analysis to characterize the transcriptional response to recombinant rainbow trout IL- 1 beta and IFN-gamma. in the trout macrophage cell line RTS- 11. Results: RNA was extracted from stimulated or control cells following 6 h incubation and used to hybridize to a salmonid cDNA microarray containing 16,006 different genes. Analysis of the arrays revealed mRNA transcripts that were differentially expressed as a result of exposure to the recombinant proteins, with some responses common for both cytokines. In general the recombinant IL- 1 beta elicited a response where genes involved in the acute phase response were upregulated, whilst the recombinant IFN- 1 beta induced strong up- regulation of genes involved in the MHC class I antigen presentation pathway. Key genes were chosen that were differentially regulated and analysed by real time PCR at additional time points, up to 48 h following stimulation. This allowed a deeper insight into the kinetics of the response to the cytokines in this cell line. Conclusion: We demonstrated that in fish both rIL- 1 beta and rIFN-gamma stimulated discrete panels of mRNA transcripts which indicted the cells were being directed towards different cellular functions, with 1L- beta inducing genes involved in the inflammatory response, whereas IFN-gamma induced genes associated with antigen presentation.