Tuberculosis infection and the repeat test. Effect in BCG-vaccinated guinea pigs.

Groups of BCG-vaccinated guinea pigs were infected with Mycobacterium tuberculosis and the course of tuberculin reactions before and after was studied. The infection led to reactions that were accelerated as if repeated tests had been given, but were larger than in such cases. Acceleration of reactions due to previous testing was present 1 week, but not 4 weeks after the start of the infection. Possibly, in cellular immunity in general, absence of the repeat test effect may be interpreted as a sign that specific antigen stimulation is taking place, and diagnostic tests could be constructed on this basis.