CD115+ monocytes protect microbially experienced mice against E. coli-induced sepsis
Matthew D. Martin, Cara Skon-Hegg, Caleb Y. Kim, Julie Xu, Tamara A. Kucaba, Whitney Swanson, Mark Pierson, Jesse W. Williams, Vladimir P. Badovinac, Steven S. Shen, Molly A. Ingersoll, Thomas S. Griffith
Abstract
Uropathogenic E . coli (UPEC) is a primary organism responsible for urinary tract infections and a common cause of sepsis. Microbially experienced laboratory mice, generated by cohousing with pet store mice, exhibit increased morbidity and mortality to polymicrobial sepsis or lipopolysaccharide challenge. By contrast, cohoused mice display significant resistance, compared with specific pathogen-free mice, to a monomicrobial sepsis model using UPEC. CD115 + monocytes mediate protection in the cohoused mice, as depletion of these cells leads to increased mortality and UPEC pathogen burden. Further study of the cohoused mice reveals increased TNF-α production by monocytes, a skewing toward Ly6C hi CD115 + "classical" monocytes, and enhanced egress of Ly6C hi CD115 + monocytes from the bone marrow. Analysis of cohoused bone marrow also finds increased frequency and number of myeloid multipotent progenitor cells. These results show that a history of microbial exposure impacts innate immunity in mice, which can have important implications for the preclinical study of sepsis.