Experimental salmonellosis: hypersensitivity to cell wall lipopolysaccharide and anti-infectious resistance of mice infected with Salmonella.

Mice infected with various strains of Salmonella enteritidis and S. typhimurium were found to be more sensitive to the cell wall lipopolysaccharide (LPS) extracted from certain strains of Salmonella than noninfected mice. This hypersensitivity was induced by those smooth or rough strains which possessed a polysaccharide chain longer than that of a glucoseless mutant. The major antigenic group participating in this hypersensitivity was presumed to be in rough core polysaccharide sequence because fractions containing either O side chain or LPS of a heptoseless mutant were ineffective in provoking a hypersensitivity reaction. Conditions for the induction and the phases of development of this hypersensitivity to LPS and for anti-infectious resistance were shown to be different. Present and previously obtained results suggest that the antigens participating in each of these two conditions were different.