Abstract
We extracted a lipopolysaccharide-like substance (LPS) from Legionella pneumophila (Philadelphia serogroup 1), and examined its chemical properties, and biological and immunological activity. The results obtained were : (1) About 70 mg of LPS was extracted from 10 g of freeze-dried L. pneumophila cultured in B-CYE-agar medium. (2) SDS-polyacrylamide gel electrophoresis yielded PAS positive bands at approximate molecular witghts of 32K and 62K dalton. These bands were also weakly stained by coomassie brilliant blue stain. (3) L. pneumophila LPS consisted mainly of penta- and hexadecanoic acid, with only slight hydroxyfatty acid. The main saccharide components were rhamnose and mannose. (4) When biological activity was compared with various LPS prepared from other sources (E. coli, S. enteritidis, and C. jejuni), the activity of L. pneumophila LSP was higher in Limulus reaction, slightly lower in pyrogenicity and comparable in both Shwartzman reaction and lethality. (5) In immunological examination, L. pneumophila LPS inhibited antibody production and showed no TNF inducing ability in mice. It had no effect on the L. pneumophila-phagocytosis of polymorphonuclear neutrophils but suppressed bactericidal action. Actions of this LPS also differed from those of other LPS in infected mice, for example, the immunological state was depressed and the lethality was increased. Since it is suspected that Legionnaires' pneumonitis is related to cellular immunity, there is a possibility that L. pneumophila LPS may give rise to the so-called immunocompromised state in which lethal infection by this strain is easily provoked.
