Damage on CNS cells elicited by innate immune activation: lessons to be learnt from the intracellular bacterium Brucella abortus.

Devoid of a lymphatic system, the central nervous system (CNS) relies primarily on innate immunity for protection. While these immune responses help to fight pathogens, they can also cause irreversible damage because of the CNS's limited regenerative capacity. Therefore, it is crucial to understand which CNS cells contribute to pathogen clearance but in doing so potentially damage surrounding tissue. Neurobrucellosis, caused by intracellular bacteria from the genus Brucella, is an inflammatory disease. Recent studies have shown that astrocytes and microglia are the source of this neuro-inflammation. In response to Brucella infection they create a microenvironment in the CNS which leads to the destabilization of the glial structure, the damage of the blood-brain barrier (BBB) and neuronal demise. Using Brucella as an example, this review of CNS glial cells responses to an intracellular bacterium shows how inflammation generates damage on tissue instead of infection resolution. Since the network of pathophysiological interactions described here are not necessarily limited to brucellosis, it is reasonable to assume that these mechanisms could be relevant in other neurological disorders in which inflammation plays a key role.