Salmonella typhimurium infection in mice: lymphoproliferative responses to fractionated protein antigens.

The proliferative response of spleen cells of mice immunized with S. typhimurium by the oral route was analyzed using antigen fractions from a protein extract of the bacteria. Mice that survived the challenge with a virulent strain of Salmonella and normal mice were also studied. Mice were immunized with three doses of live S. typhimurium on consecutive days (3C) or once a week for 3 weeks (3W). Fractions 12-100 kDa from the protein extract were separated by SDS-polyacrylamide gel electrophoresis, electroblotted to nitrocellulose membranes and processed to obtain particulate antigens for use in lymphocyte cultures. Mice immunized weekly showed a higher survival rate and responded to more antigenic fractions. We identified three fractions of 68-76, 50-52, and 42-45 kDa that were immunodominant for spleen cells from S. typhimurium immunized mice and from survivors to the challenge with the virulent strain.