Microglia-precursor cell interactions in health and in pathology

Abstract

Until recently, microglia were mainly known as the resident phagocytes of the brain, i.e. the ‘immunological warriors’ of the brain. However, extensive knowledge is being accumulated about the functions of microglia beyond immunity. Nowadays, it is well accepted that microglial cells are highly dynamic and responsive, and that they intervene in a dual manner in many developmental processes that shape the central nervous system, including neurogenesis, gliogenesis, spatial patterning, synaptic formation and elimination, and neural circuit establishment and maturation. The differentiation and the pool of precursor cells were also shown to be under microglia regulation via bidirectional communication. In this concise review, I discuss our recent work in microglia-Pax6⁺ cell interactions in one of the circumventricular organs, the pineal gland. An analogy with the rest of the central nervous system is also presented. In addition, I briefly examine mechanisms of interaction between microglia and non-microglial cells in both health and disease. New avenues are also introduced, which may lead us to better comprehend the impact of microglia in physiological and pathological conditions.