title: Mannose-binding lectin enhances the attachment and phagocytosis of mycobacteria in vitro.
abstract: BACKGROUND
  Phagocytosis is the critical first step in the Mycobacterium (M.) tuberculosis-phagocyte interaction. The process involves microbial ligands and phagocyte surface receptors. It is known that serum mannose-binding lectin (MBL), an innate immune system component, may enhance the uptake of microbes by phagocytic cells and activate the complement system. Since phagocytes are the replicative environment for mycobacteria and, as we described earlier, tuberculosis patients differ from controls in serum MBL level, we asked whether MBL plays a role in promoting M. tuberculosis access to phagocytic cells.
  
  
  METHODS
  To estimate the influence of MBL on the phagocytic process, FITC-labeled Mycobacterium bovis BCG was used as a model bacterium. Neutrophils from healthy individuals were used as phagocytes. Phagocytosis was performed in the presence or absence of recombinant MBL (rMBL; 2 or 20 microg/ml). The activation of complement was determined by dot-blot immune assay with monoclonal antibodies against C5b-C9.
  
  
  RESULTS
  We showed that phagocytosis of the bacteria was more intensive in the presence of human rMBL. Both attachment and ingestion of mycobacteria were enhanced when MBL and active complement components (fresh serum) were present in the medium. The dot-blot method showed that the bacteria slightly activated complement by themselves. This effect was enhanced in the phagocyte-bacteria co-cultures containing rMBL.
  
  
  CONCLUSIONS
  It is possible that MBL may serve in vivo as one of the factors facilitating the entry of mycobacteria into phagocytes, pathogen spread, and the establishment of infection.
authors.affiliation: Department of Immunology and Infectious Biology, Institute of Microbiology and Immunology, University of Łódź, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Bonar
authors.forename: Magdalena
authors.initials: M
authors.lastname: Chmiela
authors.forename: Wiesława
authors.initials: W
authors.lastname: Rudnicka
authors.forename: Barbara
authors.initials: B
authors.lastname: Rózalska
mesh_terms: D001422:Bacterial Adhesion; D006801:Humans; D007113:Immunity, Innate; D037601:Mannose-Binding Lectin / Q000502:physiology*; D009163:Mycobacterium bovis / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis
chemical_list: D037601:Mannose-Binding Lectin