Figure 1.

Schematic illustration of gut microbiota as potential inducer of innate memory. The gut microbial products serve as a source of microbe-associated molecular patterns (MAMPs) that bind pattern recognition receptors (PRRs) on innate cells such as monocytes/macrophages and natural killer (NK) cells. Further, this cell activation is accompanied by the epigenetic and metabolic reprogramming which is responsible for their increased cytokine release and heightened immune response upon the subsequent pathogenic exposure. Moreover, these microbial ligands reach the bone marrow through blood circulation and condition the hematopoietic progenitors to induce long-term memory traits and enhance myelopoiesis for mounting the beneficial inflammatory response during systemic infections.