NERVE GROWTH-FACTOR PRODUCTION AND EXPRESSION OF P75 BY SCHWANN-CELLSAND NEUROFIBROBLASTS IN RESPONSE TO MYCOBACTERIUM-LEPRAE INFECTION AND MACROPHAGE SECRETORY PRODUCTS

This study describes the changes occurring in vitro in nerve growth fa ctor (NGF) production and expression of p75 by murine Schwann cells an d neurofibroblasts, following infection with Mycobacterium leprae and in the presence of macrophage secretory products, using a semiquantita tive ELISA. These parameters are compared in two strains of mice, Swis s White (SW) and C57B1/6, as they differ in their response to M. lepra e infection: C57B1/6 is the 'resistant' strain. On infection, NGF leve ls remained unaltered in Schwann cells from both strains, while fibrob lasts from C57B1/6 strain showed an increase in NGF production. Expres sion of p75 by Schwann cells was decreased on infection in both strain s of mice. In vivo, this opposing effect of infection on NGF productio n and p75 expression by Schwann cells and neurofibroblasts may result in suboptimal amounts of NGF reaching neurons of the affected leprous nerves. Macrophage secretory products suppressed the production of NGF by infected neurofibroblasts from SW strain mice and the expression o f p75 in Schwann cells from both strains. These results indicate that macrophages do not assist in nerve repair in leprosy and the differenc es in response to macrophage secretory products in the two strains sug gest that different mechanisms of nerve repair operate in SW and C57B1 /6 mice and presumably in lepromatous and tuberculoid patients.