Differential expression of two pathways of chemokine induction protect CD14- and TLR4-deficient mice from localized E. coli infections (94.16)

Abstract Sepsis, characterized by a systemic bacterial infection, is a life-threatening condition that can lead to multi-organ failure and death from septic shock. We have observed that CD14- and TLR4-deficient mice are resistant to death by sepsis from several different clinical isolates of E. coli injected intra-peritoneally. This resistance has been attributed to the 10-fold lower levels of the proinflammatory cytokines TNF and IL-6 induced in these mice. Surprisingly, however, neither TLR4- nor CD14-deficient mice were resistant to two closely related organisms that differed only in that they expressed a K1 polysaccharide capsule, even though these mice continued to express low levels of the proinflammatory cytokines. These and other observations suggest that the ability to limit bacterial dissemination may be equally or even more important than reducing the levels of these proinflammatory cytokines in preventing death from sepsis. We present evidence here, that the pathogenic role for the CD14/TLR4 pathway in severe infection, whereby it mediates the induction of proinflammatory cytokines, may be secondary to a more important insidious role whereby differential activation of local and systemic pathways of chemokine induction via CD14/TLR4-dependent and independent mechanisms generate chemokine gradients that prevent PMN transmigration from the blood to infected tissue and facilitates the dissemination of bacteria from a localized site of infection.