Paper: <a href="https://doi.org/10.1038/nature25158" rel="nofollow">https://doi.org/10.1038/nature25158</a><p>The research noted here improves the understanding of how inflammation acts to drive the progression of Alzheimer's disease, despite being secondary to the well-known deposition of amyloid-β observed in the condition. Alzheimer's disease is considered to be in part an inflammatory condition. Rising levels of chronic inflammation occur with aging, in the brain and elsewhere in the body, and there is plenty of evidence for inflammation to contribute to a good many age-related conditions. The ordering of cause and effect in Alzheimer's is still somewhat up for debate, but there is evidence for the cascade to begin with amyloid-β, that then produces inflammation as the immune cells of the brain react to it, which in turn leads to tau aggregation. The paper here adds nuance to that possible ordering, suggesting that amyloid-β and inflammation form their own feedback loop, spurring one another forward.<p>The immune system of the central nervous system is its own creature, quite different in its details from the immune system of the rest of the body, and arguably much more integrated and necessary for the correct function of the brain than is the case in other organs. Nonetheless, similar classes of age-related dysfunction arise, and inflammation is one of the results regardless of protein aggregation such as the formation of amyloid deposits. Immune cells become overly active, but at the same time less effective at carrying out their assigned tasks. Inflammation is a necessary part of the immune response to many of the issues it might have to deal with, typically those that involve destruction, as as removal of senescent or potentially cancerous cells, and mounting attacks upon the pathogens that constantly try to invade the body and brain. If permanently switched on, however, inflammation begins to disrupt all of the other necessary tasks of the immune system, such as those relating to regeneration or shepherding the correct function of brain cells.<p>For a number of years now, some researchers have departed a little way from the mainstream focus on removal of amyloid-β to consider an anti-inflammatory approach to building therapies for Alzheimer's, but this line of research hasn't made a sizable impact yet. Reducing inflammation in a usefully targeted way is still quite challenging, as the immune system is very complex, though promising noises are emerging from research groups investigating NLRP3 as a target. That also happens to show up in the research here as a part of the connection between immune cells, amyloid, and inflammation.