title: Opsonic activity of plasma fibronectin for Staphylococcus aureus by human alveolar macrophages: inefficacy of trypsin-sensitive staphylococcal fibronectin receptor.
abstract: The binding of 125I-fibronectin (FN) to some bacteria and the phagocytic activity of human alveolar macrophages (AM) by a culture method using 3H-labelled bacteria were examined. FN-binding of Staphylococcus aureus (S. aureus) was higher than that of gram-negative rods and was reduced markedly by trypsin-treatment. FN enhanced the uptake of S. aureus by AM in dose dependent manner. To determine whether FN-binding to S. aureus mediates the promotion of staphylococcal phagocytosis, we compared the uptake of non-treated S. aureus with that of trypsin-treated bacteria by AM. No significant difference was found between the uptake of these bacteria and no effect of FN-binding to S. aureus on the phagocytic activity. It is concluded that FN plays an essential role as a non-immune opsonin for S. aureus in the human lung which is found to be abundant in FN, and that FN-binding to S. aureus is probably not related to this effect.
mesh_terms: D004705:Endocytosis; D005353:Fibronectins / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008264:Macrophages / Q000502:physiology*; D009895:Opsonin Proteins; D011485:Protein Binding; D011650:Pulmonary Alveoli / Q000166:cytology; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000502:physiology; D012907:Smoking; D013211:Staphylococcus aureus
chemical_list: D005353:Fibronectins; D009895:Opsonin Proteins; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic