Pattern Recognition Receptors in Brain: Emphasis on Toll Like Receptors and their Types

The immune system is highly complex; it senses foreign invaders, thus protecting the body. The adaptive arm of the immune system confers long-term protection, whereas the innate immune system confers immediate protection. In the case of the immune system, the pattern recognition receptors offer various modes of sensing the pathogen-associated molecular patterns present in pathogens. The receptors that sense invading pathogens are called Pattern recognition receptors [1]. The adaptive immune system is very sophisticated, as it is trained to identify only the “specific antigen”, but PPRs are customised to sense a wide array of “common patterns” present in the pathogens. Cerebral pericytes are the cells that are seen as embedded in the basement membrane of capillaries. Matzinger [2] gave a new insight into the recognition of pathogens by PRRs as those that recognise PAMPs and DAMPs (Damage Associated Molecular Patterns). While PAMPs can be presented as exogenous ligands to the receptor, DAMPs are presented as endogenous ligands. Once these PRRs are activated either by PAMPs or DAMPs, they lead to the production of inflammation to clear the infection. However, over-activation during chronic conditions leads to pathological changes.