Innate immunity in the adult mammalian heart: for whom the cell tolls.

Recent studies suggest that the heart possesses an intrinsic system that is intended to delimit tissue injury, as well as orchestrate homoeostatic responses within the heart. The extant literature suggests that this intrinsic stress response is mediated, at least in part, by a family of pattern recognition receptors that belong to the innate immune system, including CD14, the soluble pattern recognition receptor for lipopolysaccharide, and Toll like receptors-2, 3, 4, and 6. Although this intrinsic stress response system provides a short-term adaptive response to tissue injury, the beneficial effects of this phylogenetically ancient system may be lost if myocardial expression of these molecules either becomes sustained and/or excessive, in which case the salutary effects of activation of these pathways may be contravened by the known deleterious effects of inflammatory signaling. Herein we present new information with regard to activation of innate immune gene expression in the failing human heart. Taken together, these new observations provide provisional evidence that the innate immune system is activated in human heart failure, raising the interesting possibility that this pathway may represent a target for the development of novel heart failure therapeutics.