CD11b is required for the resolution of inflammation induced by Bordetella bronchiseptica respiratory infection

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Abstract
CD11b is a cell surface receptor that contributes to many cellular processes which are involved in the generation of a protective immune response against pathogenic organisms. In this work, the natural host-pathogen model of murine Bordetella bronchiseptica infection was used to explore the role of CD11b in respiratory immunity. Following intranasal inoculation, CD11b-/- mice rapidly succumb to B. bronchiseptica respiratory infection, highlighting the prominent role of CD11b in the generation of a protective immune response in this model. CD11b appears to be required for both the control of bacterial numbers and the regulation of cellular responses in the lungs. An increased accumulation of neutrophils in the lungs of CD11b-/- mice as compared with wild-type mice suggests that CD11b contributes to the regulation of cellular responses to respiratory infection. This accumulation may be explained by a decrease in apoptosis that is observed in the absence of CD11b following cellular interactions with B. bronchiseptica. Interestingly, this role for CD11b in the regulation of cellular accumulation appears to be critically important for the resolution of damage associated with the type III secretion system (TTSS) of B. bronchiseptica. These data provide new insight into the key role CD11b plays in the resolution of damage in the lower respiratory tract, as well as the B. bronchiseptica virulence determinant that induces it.