Abstract
Hartley 1 observed that guinea pigs injected with diluted toxoid attained a higher immunity to diphtheria toxin than those receiving an equivalent amount of undiluted toxoid. These results were confirmed by Timmerman and Brandwijk. 2 The present study was fourth, and one between the fourth and sixth. All save 2 of those responding to the first dose of toxoid ultimately showed relatively higher levels of antitoxin, that is, over 2 units.
All 15 individuals who did not respond until after the second injection showed rises in titer within 3 weeks after the second dose of toxoid. After the third dose, all but 3 showed further increase. The highest levels reached by these 15 were on the average substantially lower than for those who responded to the first dose of toxoid, but there was no significant difference between the groups.
On the final titration, all members of both groups had fallen from the highest point, but retained significant amounts of antitoxin.
Two individuals who had been previously immunized with toxin-antitoxin were among those responding to; the first injection of toxoid. Two others who had had diphtheria responded to the second dose and showed no significant variations in immune response from others in their groups.
Taken by and large, no differences were observed either in rapidity of response or in amount of antitoxin produced between a group of young adults treated with undiluted diphtheria toxoid and a comparable group given the same toxoid diluted 10 times with normal saline. Furthermore, the rate of loss of antitoxin from the blood stream was about the same in both groups although individuals varied greatly in this respect.
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