In the immunocompetent host, Mycobacterium avium is responsible for chronic localized pulmonary disease, which is characterized by the presence of increased numbers of activated T cells and macrophages in the lungs. M. avium organisms as well as sonic extracts of M. avium were found to act as chemoattractants for THP-1 cells as well as monocytes, monocyte-derived macrophages and alveolar macrophages obtained from normal human donors in an in vitro chemotaxis assay, where a significantly higher number of cells were found in wells containing M. avium compared to control wells. Proteolytic treatment of M. avium sonicate resulted in significant loss (50%) of chemotactic activity. Monoclonal antibodies against recombinant human monocyte chemoattractant protein-1 (MCP-1) were found to cross-react with a 34-kDa protein of M. avium sonicate on Western blot and inhibit M. avium sonicate-mediated chemotaxis of THP-1 cells (47%). These data suggest the presence of an 'MCP-1 like' molecule on M. avium. Recruitment of host immune regulatory cells to the site of infection by pathogens may be involved in generating a local immune response or may be a bacterial strategy for survival within the host by recruiting the cells that they infect, i.e. macrophages.
Bibliographical noteFunding Information:
This research was aided by grants from the American Lung Association (RG-082-N) and American Lung Association of California ® –Research Program to S.P.R. We thank Dr. A.G. Rao, Pioneer Hi-Bred International, Inc., Johnston, IA, USA for helpful suggestions during the course of the study.
Copyright 2008 Elsevier B.V., All rights reserved.
- Alveolar macrophage
- Monocyte chemoattractant protein-1-like protein
- Monocyte-derived macrophage
- Mycobacterium avium