Epigenetic programming during monocyte to macrophage differentiation and trained innate immunity

Monocyte differentiation into macrophages represents one of the cornerstone processes in innate host defense. In addition, immunological imprinting of either tolerance or trained immunity after an initial infection determines the functional fate of innate immune cells and the susceptibility of the host to secondary infections. Here we comprehensively characterize the epigenetic profiles of these functional states relative to healthy adult naïve monocytes. Inflammatory and metabolic pathways are strongly modulated in the derived macrophages, including decreased activation of inflammasome components. The cAMP-dependent signaling pathway is remodeled and adrenergic signaling was functionally implicated in trained innate immunity induction in vivo. Interestingly, -Glucan trains innate immune cells through extensive remodeling of distal regulatory region-bound histone acetylation, resulting in a sizeable exclusive epigenomic signature. Accordingly, genome-wide transcription factor footprint analysis reveals a specific transcription factor repertoire at trained cell-specific enhancers when recouped with epigenetic data, forming a rich hypothesis generator to manipulate innate immunity.