Isotype of protective anti-Salmonella antibodies in experimental mouse salmonellosis.

Mice and a rabbit were immunized with heat-killed Salmonella typhimurium bacteria or with an O-4,12 antigen-specific octasaccharide-protein conjugate. Immunoglobulin isotypes of the antisera were tested for their capacity to protect mice against experimental salmonellosis. Antibodies of immunoglobulin M + A isotypes were more protective than the immunoglobulin G antibodies in each of the two pools of mouse sera. The same protective pattern was also seen with a rabbit antiserum elicited by the artificial octasaccharide-protein conjugate, i.e., with antibodies with the exclusive specificity for the O-4,12 antigen determinants of S. typhimurium.