O sistema imunologico do cerebro

The Immunological System of the Brain
Besides neurons, the brain possesses a variety of support and immune cells, varying in its size, shape and function, called neuroglial cells. Although they do not directly interact in the electrical signaling and synapses, they are necessary to maintain a properly functioning nervous system. In the Central Nervous System (CNS), astrocytes, oligodendrocytes and microglial cells are all glial cells that have different but essential functions. This paper focuses on the role of microglial cells, which are responsible for protecting the brain against inflamations and pathologies, and repairing damages in the neural system caused by inflamations or diseases. In this way, they allow the CNS to keep working properly.
Microglia originate from hematopoietic stem cells in the bone marrow (Kaur, 2001). Some monocytes go from the bone marrow to the CNS through different routes (blood stream, ventricular lumen or meninges) during embryonic development (Cuadros, 1998). When they enter the brain they have an ameboid form to travel through the nervous tissue until they reach their final location, where they keep differentiating into ramified microglial cells (Cuadros, 1998).
One interesting aspect of microglia immunological activity is that some are usually “resting”, or in a quiet state, becoming activated in response to damage or injury in the CNS (Nimmerjahn, 2005). However, this quietness of the microglia shows that they are watching for changes in the nervous system environment. In fact, their reactivity and activation in response to changes in the neural environmet is very quick and efficient, which makes it an important factor in the protection of the CNS against infections, inflamations, trauma, tumors, and neurodegeneration (Kreutzberg, 1996). They respond to the early stages of brain injuries by undergoing functional and morphological transformations when changes in the structural integrity of the CNS are detected. They also ensure