Development of delayed hypersensitivity responses in Mycobacterium lepraemurium infections in resistant and susceptible strains of mice.

C57Bl mice are relatively resistant to a moderate subcutaneous infection with Mycobacterium lepraemurium while BALB/c mice are much more susceptible. Cutaneous delayed hypersensitivity reactions which develop in the first 3 weeks of infection were compared in these two strains of mice. Both strains gave a peak of delayed hypersensitivity between 6 and 10 days after infection which was followed by a period of low reactivity before the development, in the third week, of a stable persistent delayed hypersensitivity reaction. There was no difference between the strains in the size at 24 h of the delayed hypersensitivity reaction but the reactions differed in their kinetics. The low resistance strain, BALB/c, gave a Jones-Mote-type of response while the high resistance strain gave a response which could be described as a tuberculin-type reaction.