Lung surfactant protein A (SP-A) enhances serum-independent phagocytosis of bacteria by alveolar macrophages.
Surfactant protein A (SP-A) is the main protein component of lung surfactant. We studied the involvement of SP-A in body defense, i.e., effect of SP-A on the phagocytosis of bacteria by alveolar macrophages. We show here that SP-A enhances the phagocytosis of some non-opsonized bacteria: Escherichia coli growing logarithmically (E. coli/log), Pseudomonas aeruginosa/log as well as from stationary phase (P. aeruginosa/stat) and Staphylococcus aureus/log. Furthermore, not only serum-independent phagocytosis was effected by SP-A but also phagocytosis of serum-opsonized S. aureus/stat. No effect of SP-A on phagocytosis was observed with E. coli/stat neither on serum-independent nor on serum-dependent phagocytosis and on phagocytosis of non-opsonized S. aureus/stat. Thus, effect of SP-A on phagocytosis is dependent on bacterial species and on the growth phase of the microorganisms, and this effect is concentration dependent. We studied two different human recombinant SP-As and SP-A isolated from lung lavage material from proteinosis patients. These SP-A molecules contain different isomeric chains, and they differ in complexity of their structure. Qualitatively, we found the same effect with all three substances. Quantitatively, the proteinosis SP-A that forms the most complex structure was the most effective. Taken together, we demonstrated a stimulating effect of SP-A on serum-independent as well as on serum-dependent phagocytosis of bacteria by alveolar macrophages, both depending on species and growth phase of the bacteria.
Manz-Keinke
H
H
Faculty of Biology, University of Konstanz, Konstanz, Germany.
Plattner
H
H
Schlepper-Schäfer
J
J
D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000276:immunology; D018407:Bacterial Physiological Phenomena; D002455:Cell Division; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects / Q000276:immunology / Q000502:physiology; D006023:Glycoproteins / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000276:immunology; D009895:Opsonin Proteins / Q000276:immunology; D010587:Phagocytosis / Q000187:drug effects* / Q000276:immunology; D011510:Proteolipids / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000276:immunology / Q000502:physiology; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000494:pharmacology*; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000276:immunology / Q000502:physiology
D016895:Culture Media, Serum-Free; D006023:Glycoproteins; D009895:Opsonin Proteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D011994:Recombinant Proteins