Systems Biology and Innate Immunity

The innate immune system is the first line of host defense against invading microorganisms and is essential for maintenance of host health. The innate immune response is largely mediated by soluble host factors—such as complement—and phagocytic leukocytes. Cells of the innate immune system are equipped to recognize a diversity of pathogens through pattern recognition receptors present on the cell surface. In addition, deposition of complement and antibody on the microbial surface enhance the phagocytic process. The ability of phagocytes to ingest and kill pathogenic microorganisms is immediate, non-specific and not dependent on previous exposure to microbes. The innate immune response plays a pivotal role in initiating inflammation, and regulation of this critical process is highly complex. Over the past decade, our understanding of complex biological processes—including the molecular mechanisms of innate host defense—has increased dramatically through the application of systems biology-level approaches. For example, genome-wide transcript analyses and proteomics studies have been instrumental in dissecting complex signal transduction pathways involved in recognition and killing of bacterial and fungal pathogens by cells of the innate immune system. In addition, similar strategies have been used to elucidate a diversity of host pathways involved in defense against viral pathogens. This issue of the Journal of Innate Immunity highlights the use of systems biology approaches to better understand innate immunity.