Adjuvant actions of linear mannan-possessing lipopolysaccharide (LPS) in LPS-resistant C3H/HeJ mice.

Immunopotentiation has been demonstrated when Klebsiella O3 lipopolysaccharide (KO3 LPS), which possesses a linear mannan as the O-specific side chain, was injected subcutaneously into endotoxin resistant C3H/HeJ mice together with soluble protein antigens. The LPS exhibited significantly positive adjuvant effects on antibody responses in vivo after secondary antigen challenge and on delayed-type hypersensitivity (DTH) reactions against protein antigens. However, KO3 LPS was not a polyclonal B cell activator (PBA) in C3H/HeJ mice nor mitogenic in cultures of spleen cells of C3H/HeJ. Thus, the activity of the LPS in C3H/HeJ mice is confined to the potentiation of T-dependent immune responses. The contribution of the mannan O side chain to the adjuvant action of KO3 LPS was suggested.