DIFFERENTIAL IN-VITRO MODULATION OF SCHWANN-CELL PROLIFERATION BY MYCOBACTERIUM-LEPRAE AND MACROPHAGES IN THE MURINE STRAINS, SWISS WHITE AND C57BL 6/

The special susceptibility of Schwann cells (SCs) to parasitization by M. leprae and of macrophages to M. leprae-induced defects implicates them in leprous nerve pathogenesis. SC proliferation is an important p rerequisite for peripheral nerve regeneration and is regulated by a nu mber of secretory factors. Several of these factors are secreted by SC s themselves as well as by the macrophages which are recruited at the site of lesion to assist in regeneration. SC proliferation, as indicat ed by H-3-thymidine incorporation, was therefore studied in response t o M. leprae infection and in the presence of macrophages in order to d etermine the role of SC in leprous neuropathy. Cells derived from two strains of mice; Swiss White (SW) and C57Bl/6 were used, as macrophage s from these strains have been shown to differ in their response to M. leprae; such differences are similar to those observed in macrophages from lepromatous and tuberculoid leprosy patients, respectively. Infe ction with M. leprae for a duration of 9 days resulted in reduced prol iferation of SCs from SW strain, while SCs from C57Bl/6 remained unaff ected. However, in the presence of macrophages, SCs from both strains not only showed enhanced proliferation, but SW SCs also overcame the M . leprae-induced suppression of their proliferation. Altered SC prolif eration, therefore: can be implicated as a factor in leprous nerve pat hogenesis. The strain variation observed in the response of SCs indica te different nerve damage mechanisms in lepromatous and tuberculoid pa tients.