Distinctive cytokinetics of blastogenic responses by spleen cells fromLegionella pneumophila-sensitized mice

Abstract

Legionella pneumophila, the etiologic agent of respiratory pneumonia and systemic infections of man and some experimental animals, was studied in regard to the ability of these bacteria to induce blastogenic responses by spleen cells from normal vs sensitized mice. Antigens from this organism, including whole cell vaccine, an outer membrane extract, and a purified lipopolysaccharide-rich antigen, induced blastogenesis of normal spleen cells with peak responses on day +3 in vitro, similar to the blastogenic responses of spleen cells from the same animals exposed to the plant mitogens phytohemagglutinin and Concanavalin A, or the nonspecific bacterial antigenEscherichia lipopolysaccharides coli (LPS). Spleen cells from mice vaccinated with killedLegionella or infected with a sublethal dose of these bacteria 3–4 weeks or more previously evinced increased blastogenic responses to theLegionella antigens but not to the nonspecific mitogens or theE. coli LPS. The spleen cells from legionellae-sensitized mice evinced not only heightened blastogenic responses on day +3 of culture but also heightened responses during day +5 of culture. Spleen cells from sensitized mice showed less responses to the nonspecific plant mitogens orE. coli LPS on day +5 of culture. These results support the view that, after sensitization of mice with a bacterial antigen such asL. pneumophila, spleen cells respond in a specific heightened blastogenic manner toLegionella antigen, and this response has a higher magnitude and is more prolonged than the non-specific responses of cells from normal mice.