Blockade of eosinophil production by toll-like receptors

Abstract

It has long been known that eosinopenia is observed during acute bacterial infection yet the mechanism remains undefined. Herein, we investigated the consequence of exposure to microbial products, specfically bacterial lipopolysaccharide (LPS), on eosinophil production. We demonstrate that developing murine eosinophils transiently express mRNA for six Toll-like receptors (TLR5) with highest expression of TLR2 and TLR4 throughout eosinophil development and nearly undetectable levels on mature eosinophils. LPS stimulation of eosinophil progenitors ex vivo markedly inhibited IL-5- mediated cellular proliferation and expansion Further LPS adrninistratwn in vivo reduced numbers of eosinophil progenitors in the bone marrow and blood in mice. Notably, LPS effectively reduced eosinophilia even in hypereosinophilic mice induced by the IL-S transgene. Taken together, these findings identify a mechanistic explanation for eosinopenia following bacterial infections and a novel therapeutic strategy for depleting eosinophil progenitors and inhibiting peripheral eosinophilia in eosinophil associated diseases.

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