Abstract
A systematic qualitative and quantitative study has been made on the immunity developed in a group of young adults immunized against diphtheria with toxin-antitoxin.
As a preliminary, a successful attempt was made to corroborate Havens' contention that there are two serological groups of diphtheria bacilli with specific agglutinogenic properties and no evidence of cross agglutination. For our minor group antigen we used two cultures recovered from cases of diphtheria developed in persons immunized with toxin-antitoxin and yielding negative Schick tests.
This specificity has been further substantiated by antibody absorption, which confirms the other findings completely.
Incidentally, we used rabbit blood agar plates exclusively for isolation and study of the organisms, and noted that hemolysis, a sometime mooted point, is not characteristically allied with virulence, nor does it only occur in freshly isolated cultures, but may crop up as late as the 56th generation.
We have also found, as we believe Park stated, that certain true diphtheria bacilli possess a factor of virulence not neutralized by antitoxin, concerning whose identity we are making a further study. Likewise we have confirmed Park and Havens in finding that there is some group antitoxin present in the antitoxin commonly in use for the toxin of the minor group.
Using a modified Romer method, we titrated the antitoxin content of a group of young adults immunized against diphtheria with toxin-antitoxin. We found 20 out of 26 had developed antitoxin in quantities varying from 1/30 unit up to 1/5, while three developed only 1/50, and three failed to develop any immunity.
We then ran Schick tests with regular and minor group toxins. Without exception, all gave a strongly positive reaction to the minor group toxin, though 20 were protected completely against the regular toxin, and three more partially so.
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