Studies on the optimal immunization schedule of experimental animals. IV. The optimal age and sex of mice, and the influence of booster injections.

To establish the optimal condition for preparing mouse antiserum specific to a drug, the optimal age and sex of mice for the immune response were studied by measuring the mouse serum levels of total immunoglobulin G (IgG) and specific antibody to viomycin, as well as the changes in weight of mice immunized with a viomycin immunogen. It was observed that age was a more important factor than sex, and strongly affected productions of both total and specific IgGs of mice. The mice aged 8 weeks yielded the highest levels of both total IgG and the specific antibody. In the study on the influence of booster schedule, the number of boosters given had a larger influence on the immune response than the interval between priming and boosters. The greater the number of booster shots given, the less was the production of total and specific antibodies. The decrease in the weight of mice after immunization was also studied in more detail; it was found that it only occurred in the first week after priming but not after a booster injection. The mice aged eight weeks showed the largest weight loss.