CXCR3 and Its Ligands Participate in the Host Response toBordetella bronchisepticaInfection of the Mouse Respiratory Tract but Are Not Required for Clearance of Bacteria from the Lung

Abstract

Intranasal inoculation of mice withBordetella bronchisepticaproduces a transient pneumonia that is cleared over several weeks in a process known to require both neutrophils and lymphocytes. In this study, we evaluated the roles of the chemokines MIG (CXCL9), IP-10 (CXCL10), and I-TAC (CXCL11) and their common receptor, CXCR3. Following bacterial inoculation, message expression of interleukin-1 (IL-1), IL-6, and the neutrophil-attracting chemokines KC, LIX, and MIP-2 was rapidly induced, with maximal expression found at 6 h. In contrast, message expression of gamma interferon, MIG, IP-10, and I-TAC peaked at 2 days. Expression of all of these chemokines and cytokines returned to near baseline by 5 days, despite the persistence of high levels of live bacteria at this time. Induced MIG, IP-10, and I-TAC protein expression was localized in areas of inflammation at 2 to 3 days and was temporally associated with increased levels of CXCR3⁺lymphocytes in bronchoalveolar lavage fluid. There was no increase in mortality in mice lacking CXCR3. However, the clearance of bacteria from the lung and trachea was delayed, and the recruitment of lymphocytes and NK cells was slightly decreased, for CXCR3^−/−mice relative to CXCR3^+/+mice. We conclude that the CXCR3 receptor-ligand system contributes to pulmonary host defense inB. bronchisepticainfection by recruiting lymphocytes and NK cells into the lung.