The use of the hemagglutination technic for the measurements of diphtheria antitoxin titers.
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Diphtheria antitoxin titers were measured by the hemagglutination technic in the serums of 7 normal subjects before and after immunization with a small dose of diphtheria toxoid. The "booster" dose administered was 1 Lf of fluid diphtheria toxoid. Human Group O red blood cells treated with tannic acid and diphtheria toxoid as the sensitizing antigen were employed in the hemagglutination methods. Hemagglutinating titers were expressed in antitoxin units per milliliter of a serum when compared with the hemagglutinating titer of a known diphtheria antitoxin. On one of the 7 subjects the experiment was extended over a period of eighty-six days after the administration of the "booster" dose. The remaining 6 subjects were tested repeatedly during a period of from zero to fourteen or twenty-four days because this time proved to be sufficient for the demonstration of a secondary antibody response. In all cases a blood sample was taken before the injection of the toxoid. Schick tests had not been done for the last six months, and were avoided before beginning the experiment because the Schick toxin could have acted as an immunizing stimulus and interfered with the experiment. Five of the 7 subjects who had a certain basic immunity against diphtheria, as determined from the serum specimens obtained before the immunization, showed definite increases in hemagglutinating titers after the stimulus. In every one of 5 subjects in whom an antibody rise was observed the distribution of the hemagglutinating titers was characteristic of a secondary antibody response. One of the remaining 2 subjects had no basic immunity, and no change in titer, as determined by the hemagglutination technic, was noticable within fourteen days after the booster immunization. The other subject had a very low hemagglutinating titer before the injection of the "booster" dose, but the titer did not increase during the next eighteen days. The partial hemagglutination reactions obtained with undiluted serums on the fourth, seventh, tenth and eighteenth days after the stimulus was injected were considered as nonspecific. Five individual serum specimens were titrated by the intracutaneous rabbit method. for comparison. In two instances the correlation between the antitoxin contents as determined by both these methods was close. Generally, antitoxin values were lower when determined by the intracutaneous method. The lack of correlation could probably be explained by the great sensitivity of the hemagglutination methods; however, this sensitivity does not always rule out the possibility of nonspecific hemagglutination reactions between minor impurities in the antigen and antiserums. The hemagglutination technic used in this work enabled the estimation of as little as 0.00097 unit of antitoxin per milliliter of a serum. The method is very sensitive and proved useful for the determination of the antibody response in diphtheria immunization.
Thesis (M.A.)--Boston University