Protection against Klebsiella pneumoniae induced lobar pneumonia in rats with lipopolysaccharide and related antigens.

The immunoprotective role of lipopolysaccharide and related antigens from Klebsiella pneumoniae was studied in a lobar pneumonia model developed in rats. Various antigens were obtained by different chemical treatments of the lipopolysaccharide. All these antigens (purified lipopolysaccharide, reduced lipopolysaccharide, lipopolysaccharide--bovine serum albumin complex, and lipid A--bovine serum albumin complex were tested for pyrogenicity and the Shwartzman reaction. The lipopolysaccharide and the various related antigens were pyrogenic and elicited a positive Shwartzman reaction at high concentrations. However, at low concentrations, the same preparations did not show any side effects. All these antigens, on the other hand, were protective against bacterial challenge in Klebsiella pneumoniae induced lobar pneumonia in rats, as the bacterial colonization of lungs in the immunized animals was significantly lower when compared with the controls. The alveolar macrophages from these animals also showed significantly more uptake of Klebsiella pneumoniae as compared with those obtained from control animals.