Abstract:  

The sterility of the blood circulation is essential for  human health, but the cellular and molecular basis for microbial recognition and capture has remained largely unclear.  Recent  studies have uncovered that the resident macrophages in the liver (Kupffer cells) and spleen (red pulp macrophages) are responsible for capturing and killing blood-borne bacteria.  This sterilizing immunity requires the initial recognition of invading bacteria by pattern-recognition receptors.