Ablation of the complement C3a anaphylatoxin receptor causes enhanced killing of Pseudomonas aeruginosa in a mouse model of pneumonia

• Published in: American journal of physiology. Lung cellular and molecular physiology 2006-08, Vol.291 (2), p.L157-L165
• Main Authors: Mueller-Ortiz, Stacey L, Hollmann, Travis J, Haviland, David L, Wetsel, Rick A
• Format: Article
• Language: English
• Subjects: Animals; Antibodies - blood; Bronchoalveolar Lavage Fluid - cytology; Chemokines - immunology; Cytokines - immunology; Disease Models, Animal; Female; Lung - cytology; Lung - metabolism; Lung - pathology; Male; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Pneumonia; Pseudomonas aeruginosa; Pseudomonas aeruginosa - immunology; Reactive Oxygen Species - metabolism; Receptors, Complement - genetics; Receptors, Complement - metabolism
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00358.2005

1 Research Center for Immunology and Autoimmune Diseases, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, University of Texas Health Science Center at Houston, Houston; and 2 Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas Submitted 18 August 2005 ; accepted in final form 31 January 2006 The C3a anaphylatoxin is a 77-amino acid peptide that is generated by enzymatic cleavage of C3 during activation of the complement system. C3a mediates numerous biological functions on binding its receptor (C3aR), which is present on both myeloid and nonmyeloid cells. To investigate the biological impact of C3a-mediated effects during acute pneumonia caused by Pseudomonas aeruginosa , we subjected C3aR-deficient mice and matched wild-type (WT) mice to P. aeruginosa pulmonary infection. C3aR-deficient mice exhibited increased killing of P. aeruginosa in the lungs, less dissemination of bacteria into the bloodstream, and a decreased inflammatory response to P. aeruginosa pulmonary infection compared with WT mice. To examine whether the absence of C3aR would impact the humoral immune response to P. aeruginosa , we immunized WT and C3aR-deficient mice via intraperitoneal injection with live P. aeruginosa . Both groups of mice developed similar levels of antibody specific to P. aeruginosa. Immunized C3aR-deficient and WT mice were subjected to P. aeruginosa pulmonary infection, and C3aR-deficient mice again displayed increased killing of P. aeruginosa in the lungs, less dissemination of bacteria into the bloodstream, and a decreased inflammatory response in the lungs. Collectively, these data demonstrate that independently of antibody production, absence of C3aR causes enhanced killing of P. aeruginosa despite a diminished inflammatory response in a mouse model of pneumonia. bacteria; pulmonary; infection; inflammation; antibody Address for reprint requests and other correspondence: R. A. Wetsel, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Univ. of Texas-Houston, 2121 W. Holcombe Blvd., Suite 907, Houston, TX 77030 (e-mail: Rick.A.Wetsel{at}uth.tmc.edu )