Microglial integrin, chemokine receptors, and inflammatory response vary with development.

Understanding microglia development could improve our understanding of the central nervous system (CNS) and neurological diseases. To explore the immune phenotypic changes that occur in microglia during development, we studied the morphology, inflammatory response, and expression of several important immune-related proteins in normal microglia from the embryonic, neonatal (postnatal day 3), and adult stages. Results showed that implantation of microglia into the CNS until adulthood resulted in dynamic changes in the expression levels of CD11b (α chain of complement receptor 3) and CX3CR1 (a chemokine receptor), which were consistent and correlated. Expression of proinflammatory cytokines in microglia during development is dynamic and highest in perinatal period. The inflammatory response of microglia was more vigorous and intense in the neonatal microglia than in the adult microglia. Furthermore, the morphology and function of neonatal and adult microglia differed, and thus neonatal microglia cannot be used in lieu of adult microglia for functional studies. Taken together, our results suggest that microglial integrin, chemokine receptors, and inflammatory responses vary with developmental age, which is an important finding for studying the role of microglia in different age-related neurological diseases.