The separation of the histamine-sensitizing factor from the protective antigens of Bordetella pertussis.

The histamine-sensitizing factor of was shown by fractionation of extracts to be different from the antigen protecting mice against an intracerebral challenge. Ten per cent methanol precipitates from a calcium chloride extract of broken cells a water-soluble fraction containing the histamine-sensitizing factor and the antigen protecting mice against an intracerebral challenge. Dialysis of this fraction yields a precipitate soluble at H, containing a much greater amount of protective antigen than histamine sensitizing factor and supernatant which has high histamine sensitizing activity and is of poor immunizing potency. Antisera to the material precipitated on dialysis are fairly specific, protecting against an intracerebral challenge but not against an intranasal challenge, and do not contain anti-histamine-sensitizing factor. The supernatant is much less pure; it stimulates antibodies to the histamine-sensitizing factor and also contains both protective antigens. Sera to other fractions have been obtained, however, which protect against an intranasal challenge but do not contain anti-histamine-sensitizing factor. Although mixtures of antigens and mixtures of antibodies were used, sufficient evidence was obtained to distinguish the histamine-sensitizing factor from the two types of protective antigen. The histamine-sensitizing factor is distinct from the agglutinogen, the haemagglutinin and the toxin.