The immunologic reactivity of a lipopolysaccharide (LPS)-protein complex isolated from a potassium thiocyanate extract of a Pasteurella multocida (capsular type A and somatic type 3) strain was evaluated in mice. The LPS-protein complex provided 100% protection in mice against a challenge with the homologous strain. However, when the complex was fractionated into LPS and protein moieties by phenol-water treatment, both components lacked immunogenicity. The complex and extracted components were mitogenic for mouse B lymphocytes with the protein moiety the most active. Although immune serum against the LPS-protein complex protected mice against challenge thereby indicating a role for humoral immunity, the LPS-protein complex of P. multocida was also found to induce cell-mediated immunity. This cell-mediated immunity was demonstrated in mice immunized with the complex by: (1). mitogenic responses of T lymphocytes, (2). induction of delayed type hypersensitivity reaction in the hind footpads, and (3). enhanced resistance to challenge infection with Salmonella enteritidis.
Animals ; Antibodies, Bacterial/blood/immunology ; Bacterial Proteins/chemistry/*immunology ; Chemical Fractionation ; Hypersensitivity, Delayed ; Immune Sera/immunology ; Immunity, Cellular ; Immunization, Passive ; Lipopolysaccharides/chemistry/*immunology ; Lymphocyte Activation ; Mice ; Pasteurella Infections/immunology/*prevention & control ; Pasteurella multocida/*chemistry/immunology ; Salmonella Infections, Animal/immunology/prevention & control ; Salmonella enteritidis/growth & development/immunology ; Spleen/cytology/immunology/microbiology