Microglia is a brain-specific macrophage lineage that seeds the developing brain tissue in utero (embryonic) and contributes to "patterning and wiring of the brain in early development and contribute to homeostasis throughout life". Since brain is cocooned from the rest of the body by blood-brain barrier (BBB), it is not clear whether microglia, as a member of innate immune system, is responsive to signals generated within immune system.
New study in Science suggests that brain resident microglia undergo time-dependent step-wise upgrades and retains sensitivities to signals derived from immune system and microbiota.
Basically for this study the authors analyzed gene expression profile of microglia (both from single cell and from the pool) harvested from brain at different developmental stage (in utero (embryonic), newborn and adult).
Interestingly and relevant for medicine, the authors could show that systemic activation of immune system by poly I:C could disrupt normal formation of newborn microglia by switching its developmental program to more adult microglia-like setting.
Such changes in newborn microglia can potentially underlie neuro-developmental challenges in babies born to mothers experiencing immune activation (viral infections) during pregnancy.