Figure 5.

Neuron-associated macrophages. Neuron-associated macrophages are located in close proximity to enteric neurons within the submucous plexus and the myenteric plexus, located deep within the gut wall. Neuron-associated macrophages are largely self-maintaining, and receive little input from circulating cells. Neurons in the myenteric plexus maintain the macrophage population via production of CSF-1, which is necessary for macrophage survival. Furthermore, acetylcholine released from enteric neurons can modulate the phenotype of macrophages in the context of intestinal inflammation. Conversely, macrophages within the muscularis externa produce BMP2, which is critical for peristalsis. Selective depletion of neuron-associated macrophages leads to a loss of enteric neurons in both the myenteric and submucosal plexuses, leading to impaired intestinal contractility and impaired anion secretion. Ach, acetylcholine; aBMP2, bone morphogenetic protein 2; CSF-1, colony stimulating factor 1.