Loss of adjuvanticity in rats for the hyperacute form of allergic encephalomyelitis and for reaginic antibody production in mice of a phenotypic variant of Bordetella pertussis.

The adjuvanticity of a phenotypic (C-mode) variant of B. pertussis, known to be deficient in certain immunological and physiopathological properties, was compared to that of the normal (X-mode) strain. The X-mode vaccine was a potent adjuvant for induction of hyperacute experimental allergic encephalomyelitis to guinea-pig spinal cord in Lewis rats whereas C-mode vaccine was inactive. X-mode vaccine was also highly active in the induction of reaginic (both IgE and IgGl) antibodies to ovalbumin in mice while C-mode vaccine caused only a transitory increase in the IgE level. These data support the view that an adjuvant component of B. pertussis, which is probably identical with the histamine-sensitizing and leukocytosis promoting factor, is much diminished in C-mode cells while the lipopolysaccharide adjuvant remains unchanged.