Kupffer cell-like syncytia replenish resident macrophage function in fibrotic liver

<p class="AbstractSummary"><span>Kupffer cells (KCs) are localized in liver sinusoids but extend pseudopods to parenchymal cells to maintain their identity and serve as the body's central bacterial filter. Liver cirrhosis dramatically alters vascular architecture, but how KCs adapt is unclear. We used a mouse model of liver fibrosis and human tissue to examine immune adaptation. Fibrosis forced KCs to lose contact with parenchymal cells, downregulating "KC identity", which rendered them incapable of clearing bacteria. Commensals stimulated the recruitment of monocytes via CD44 to a spatially distinct vascular compartment. There, they formed large aggregates of multinucleated cells (syncytia) that expressed phenotypical KC markers and displayed enhanced bacterial catching ability. Syncytia formed via CD36 and were observed in human cirrhosis as a possible antimicrobial defense that evolved with fibrosis.</span></p>