Studies on the reactions of animals to infestation with ticks. III. The reactions of laboratory animals to repeated sublethal doses of egg extracts of Haemaphysalis bispinosa Neumann

Abstract

Rabbits and mice have been immunized or sensitized, and guinea-pigs sensitized, with saline extracts of the eggs of Haemaphysalis bispinosa. Immunization, without sensitization, invariably followed intravenous inoculation of the antigen once or twice per week for 3 weeks. Sensitization, with or without development of precipitating antibody, usually followed daily inoculation for 3 to 5 days, subcutaneous administration possibly being more effective than intravenous. Development of sensitization was capricious. Immunized animals were protected against the toxic egg extracts, but not against attachment of larval ticks. Their sera contained complement-fixing and precipitating antibody, which was not destroyed at 56°C for 4 hr. Sensitizing antibody could not be demonstrated in these sera by direct skin test or passive transfer. Sensitized animals responded to intradermal injection of antigen by a characteristic skin reaction, and were protected against effective attachment of larval ticks. Sensitization could be transferred passively by subcutaneous inoculation of serum, and was not reduced by absorbing out any precipitating antibody that may have been present. The sensitizing antibody was destroyed by heating to 56°C for 4 hr. In passive transfer tests, sera of immunized animals blocked local reaction to antigen in sensitized animals, but the blocking antibody rapidly diffused from the site, whereas sensitizing antibody remained fixed. Electrophoretic evidence suggests that the immune antibodies are principally y-globulins, whereas the sensitizing antibodies are mainly ß-globulins.