Interferon production in mice by the capsular polysaccharide of Klebsiella pneumoniae.

The capsular polysaccharide of Klebsiella pneumoniae (CPS-K) type 1, Kasuya strain, induces interferon production in the blood of mice when injected intravenously. CPS-K resembles bacterial endotoxin (lipopolysaccharide) in the time pattern of interferon production, with peak levels 2h after injection. CPS-K on a weight basis exhibits a more potent interferon-inducing effect than lipopolysaccharide. The active substance responsible for the interferon-inducing activity of CPS-K is the neutral CPS-K antigen which is antigenically distinct from the O antigen and from acidic CPS-K (the type-specific capsular antigen). Neutral CPS-K from the Kasuya strain has been already found to exhibit a strong adjuvant effect on antibody responses to various antigens in mice. Preparations of neutral CPS-K from other strains of K. pneumoniae, of which adjuvant action is only very weak, exhibit interferon-inducing activity similar to the preparation from the Kasuya strain. Heterologous and homologous tolerance to re-induction of interferon is produced by a prior injection (one each) of LPS, neutral CPS-K, and acidic CPS-K. No simple correlation exists between the inducing and tolerogenic capabilities of these substances.