Abstract
The relationship between M. leprae and peripheral nerves has been studied since the beginning of the scientific research of leprosy by many workers, especially from histo-pathological point of view.
In this paper we present the data of our experimental studies concerning the affinity of M. leprae to peripheral nerves. We have studied this problem by the following experiments and observations, i. e. "Intraneural inoculation of acid-fast bacilli, " "Tissue culture of leprous peripheral nerves" and "Biomicroscopy of leprous corneal nerves" etc.
1) Intraneural inoculation of acid-fast bacilli.
We inoculated M. leprae, M. leprae murium, Tubercle bacillus (human, bovine and avian types), B. C. G., M. ulcerans, Smegma bacillus in sciatic nerves of rabbits, guinea-pigs, rats and monkey, and examined histo-pathologically the affinity of these acid-fast bacilli to the peripheral nerves of these mammalians.
We have found that acid-fast bacilli multiply in peripheral nerves of susceptible animals, especially in the endoneurial cells. For instance, M. leprae murium causes intraneural leprom in the sciatic nerves of rats, when inoculated directly in these nerves. Tubercle bacillus multiplies in the sciatic nerves of susceptible animals, and makes tuberculous lesions in these nerves. M. leprae does not multiply in. the peripheral nerves of monkey, rat, guinea-pig and rabbit. The most strong lipoid degeneration was observed in the lesions of intraneural inoculation of M. leprae into rabbits. Strong calcification occurs very often, when smegma bacillus is inoculated into the sciatic nerves of rabbits.
2) Tissue culture of the leprous peripheral nerves.
We have cultured 14 biopsy specimen of leprous peripheral nerves in vitro, and examined the possibility of multiplication of M. leprae in the growing cells.
Endoneural fibroblasts are most frequently seen in the tissue culture of lepromatous nerves, on the contrary tuberculoid nerves show scanty cell growth in vitro. Sometimes small number of M. leprae was found in the growing cells, but we could not conclude from such finding the multiplication of M. leprae in vitro. The growth of Schwann cells as observed frequently in the tissue culture of normal peripheral nerves was rarely encountered in the culture of leprous nerves. This fact is perhaps related to the deficiency of nerve regeneration in leprosy cases.
3) Biomicroscopy of leprous corneal nerves.
We have examined biomicroscopically the corneal nerves of leprosy patients and confirmed the "beaded corneal effect" in both lepromatous and tuberculoid cases. This finding indicated the affinity of M. leprae to the peripheral nerves of both polar types of leprosy.
We have also examined the corneal nerves of rabbits by polarizing microscope and found that there is a thin bi-refringent layer over the axon even in the so-called amyelinated portion of corneal nerves.
4) Histo-chemical study of leprous peripheral nerves.
In the tuberculoid nerves both acid and alkaline-phosphatase were found histochemically, and in case of lepromatous nerve lesions we have found acid phosphatase, but no alkaline phosphatase was confirmed. We think alkaline phosphatase in tuberculoid nerve lesions might play a role in the calcification of tuberculoid nerve lesions.
5) Study of the nerve regeneration in leprous nerves.
We examined the nerve stump of re-amputated legs of leprosy cases with polarizing microscope, and found that this microscope is very convenient to trace the remaining myelin sheath in the highly degenerated nerves.
6) Summary and conclusion.
M. leprae has an affinity to the axon in both lepromatous and tuberculoid leprosy, and after reaching peripheral nerves, it causes different lesions according to the tissue resistance of the individual toward this microbe.
