MITSUDA-TYPE LEPROMIN REACTIONS AS A MEASURE OF HOST-RESISTANCE IN MYCOBACTERIUM-LEPRAEMURIUM INFECTION

The footpad reaction to autoclaved whole M. lepraemurium organisms (MLM lepromin) in high-resistance (C57BL) and low-resistance (BALB/c) mice was studied. Infected C57BL mice gave a prolonged footpad response persisting for 4 wk after skin testing with high and low doses of lepromin. This was accompanied by mononuclear cell infiltration. Uninfected C57BL mice gave no response. The majority of infected BALB/c mice gave no increase in footpad thickness. A high proportion of infected and control BALB/c mice tested with the high dose showed mononuclear cell infiltration which resembled that in C57BL mice. The low dose caused little infiltration in infected or control BALB/c mice. The course of infection in the 2 strains was different. Dissemination of organisms from the infected footpad was minimal in C57BL mice 5 mo. after infection. In BALB/c mice, dissemination to the draining lymph node and to some extent to the liver had occurred by 5 mo. The draining lymph node of BALB/c mice showed histological evidence of local antibody formation, which was not found in C57BL mice. Murine leprosy in these 2 strains could be fitted into a classification similar to that used for human leprosy.