Mikrogliat

Mikrogliat are the resident immune cells of the central nervous system and a specialized type of glial cell. They originate from yolk sac progenitors that migrate into the brain during early embryonic development and establish the CNS's innate immune population. In the adult brain, mikrogliat maintain their numbers mainly through local self-renewal, with limited replacement from circulating monocytes except after injury or disease.

Morfology and markers: in healthy tissue mikrogliat have small cell bodies with highly branched, motile processes that continuously survey their environment. They express a set of molecular markers used in research, including IBA1, CX3CR1, and TMEM119 in humans, with P2RY12 commonly cited as a microglia-specific marker in the healthy CNS.

Functions: mikrogliat perform immune surveillance, phagocytose cellular debris and misfolded proteins, and secrete cytokines and chemokines in response to injury or infection. They participate in synaptic pruning during development by marking and removing weak or unnecessary synapses, contributing to the maturation of neural circuits. They also interact with astrocytes and the vasculature to regulate the blood-brain barrier and CNS homeostasis.

Development and heterogeneity: during development they populate the CNS and adapt to regional environments. In adulthood they exhibit regional differences and functional diversity, a subject of active research. Studies use single-cell sequencing and imaging to characterize microglial states beyond the historical M1/M2 dichotomy.

Clinical relevance: dysregulated mikrogliat activity is linked to neuroinflammation and a range of neurological disorders, including neurodegenerative diseases such as Alzheimer's disease, multiple sclerosis, and other conditions. In disease, microglia can contribute to pathology through chronic cytokine production, synaptic remodeling, and interactions with amyloid plaques and damaged neurons. Understanding microglial biology informs potential therapeutic approaches targeting CNS immunity.