Dominance of E. coli phagocytosis over LPS in the inflammatory response of microglia.

CNS bacterial infections are prevalent in neonates, the immune-compromised and elderly. During peripheral infections, macrophages employ multiple pattern recognition receptors (PRRs) to respond to pathogens, but less is known about brain microglia. We assessed microglial expression of PRRs, compared responses to whole E. coli and LPS, and tested the hypothesis that bacteria modulate the response to LPS. LPS increased the microglial phagocytic capacity, and changed expression of CD14, CR3, Fcgr1, Fcgr3a, TLR4, MARCO, MHCII, NOD2, TLR9 and SR-A, differently from stimulation with whole E. coli. Importantly, when added with LPS, E. coli dominated the microglial responses for 11/13 genes examined.