Influence of Route of Mycobacterium lepraemurium Injection on Susceptibility to Mouse Leprosy and on Lymphoblastic Transformation

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Abstract
Groups of female C57BL/6 and C3H/St mice were inoculated i.p. with 109, 107 and 105 bacilli and into the right hind footpad with 107 and 105 bacilli of M. lepraemurium. The incidence of death from leprosy and the mean survival time of leprous mice were recorded. Blastogenic responses to the T [thymus-derived] cell mitogens phytohemagglutinin and concanavalin A and to the B [bone marrow-derived] cell mitogens lipopolysaccharide and dextran sulfate were evaluated at various times during the course of infection in the spleen and peripheral lymph nodes of mice infected with 107 bacilli. When M. lepraemurium was administered i.p., the 2 mice strains succumbed to the disease at about the same time, except for the C57BL/6 mice infected with 109 bacilli, which died earlier than the C3H/St mice. In both mice strains progressive depression of blastogenesis, first to the T cell mitogens and then to the B cell mitogens in the spleen, and to the T cell mitogens in the peripheral lymph nodes, occurred during the infection, whereas the response to the B cell mitogens in the nodes increased slowly during the advanced stage of the disease. When 107 and 105 bacilli were injected into the footpad, the C3H/St mice succumbed to the disease at 298 and 344 days, respectively, and the modifications of blastogenesis were similar to those observed in i.p.-infected C3H/St mice. The C57BL/6 mice appeared resistant to footpad inoculation of M. lepraemurium, since they lived until the end of the observation period (466 days post-infection) and the depression of blastogenesis was not detectable until 1 yr after the infection. For C57BL/6 mice (but not for C3H/St mice), the route of administration of M. lepraemurium can markedly influence susceptibility or resistance to leprosy.