Abstract
In the course of observing various reactions associated with spontaneous survival of guinea pigs infected experimentally with pneumococcus Type I the appearance and rise of protective antibody in the blood has been studied. The animals were infected by intra-abdominal injection of 0.25 cc of an 18-hour serum-dextrose-broth culture of pneumococci. Under these conditions and without treatment 47 of 100 animals survived. The day of recovery of the animals has been considered as being identical with the day a negative culture of the peritoneal exudate was obtained. Only surviving animals were studied, since the majority which did not survive, died before the fourth day.
Blood was taken from the heart of the guinea pigs at various intervals and the serum separated. The tests were carried out by determining the number of minimal lethal doses of a virulent Type I pneumococcus which could be neutralized by 0.5 cc of the serum when mixtures of the culture and the serum were injected intraäbdominally into mice.
It was not possible to take blood from the guinea pigs for testing of protective titer at daily intervals so that there are of necessity some intervals which have not been thoroughly explored, but the studies are probably sufficiently detailed to warrant certain conclusions.
Forty-two of 47 guinea pigs which survived the infection are considered here. Serum for antibody-titration was obtained from all animals before infection. Only one animal showed the presence of antibodies; they were no longer demonstrable by the fifth day of infection and did not reappear during the period of observation (through the 24th day).
In Table I is shown the relation between the appearance of antibodies and the recovery from infection as measured by the negative peritoneal culture. In only a very few cases was blood taken for testing antibodies on the second day after infection, and in no animals were protective antibodies demonstrable.
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