Deformity of feet, e.g., shortening of fingers and absorption of phalanges was observed in 19 (6.5%) out of 291 mice of dd-strain on more than 3 months after the subcutaneous inoculation of M. leprae into the foot-pad. The M. leprae for inoculation were isolated from four untreated leprosy patients, and from one treated patient. These deformities were observed mainly in the rear-foot, but the front-foot was also involved in 2 of the mice who showed deformity, although the organisms had been inoculated in the rear-foot only. The mice were kept under observation for a period of two years, but no deformity other than those noticed during the first 3-6 months could be observed. Histopathologically the degeneration of phalanx-bones with the increase of osteoblasts and periostal tissue was observed; there was hardly any inflammatory response to infection. In order to investigate on the cause of these deformities of feet, Mitsuda antigen, saline emulsions of human skin and the skin of some animals, adjuvants, oils, Tween 80, Gum arabic, Polyethylenglycol, Albumin, Casein, Dextran, cellulose, mucin and enzymes were injected subcutaneously into mice foot-pad. The inoculation with these materials caused no adsorption of the phalanx-bones and no deformity except the necrosis of local tissue resulting from the injection of foriegn material. Even the inoculation of M. leprae isolated from a treated leprosy patient caused no deformity in the mice. However, swelling of the foot-pad at the site of inoculation was observed with the injection of M. lepraemurium, and the inoculation of the other mycobacteria into mice foot-pad induced no deformities. Injection of mycobacteria and adjuvant mixtures caused the deformity only in case of M. fortuitum which gave rise to abscess formation and absorption of phalanxbones. However, these deformities were different from the findings of feet observed in mice who were inoculated with M. leprae. Among the non-inoculated control mice living in the same cages as the inoculated deformed mice, no deformities could be observed which indicates that the process was not infective in nature. The above experiments were performed with five strains (e.g., dd-, ddN-, ICR-, C3Hand hybrid offsprings of C3Hand dd-strain) of mice. One of those, only the mice of dd-strain, showed the deformities as a result of foot-pad inoculation with M. leprae. This fact indicates that the hereditary factors may be involved in the causation of these deformities. The genetical aspect is now being further investigated by breeding the mice of dd-strain in which the deformity had been observed. These experiments show that the causation of the deformities, described above, in the dd-strain of mice is probably a phenomenon specific to M. leprae.
Kazunari Nakamura, M. Maeda, K. Maruyama
Journal name not available for this finding