Study of concanavalin A receptors on macrophages in leprosy

Increasing evidence suggests an immunosuppressive role for the macrophages in lepromatous leprosy. Alteration in the surface membrane is often reflected in the ability of the macrophage to initiate an immune response. We have used the Concanavalin A (Con A) receptor on macrophages as one of the markers for the study of membrane changes in leprosy. The data presented demonstrates that on in vitro infection with M. leprae the percentage of macrophages demonstrating the presence of Con A receptors remains unaltered in macrophages from normal individuals as well as from tuberculoid leprosy patients. However, in the bacteriologically negative lepromatous patients there is a significant reduction in the percentage of receptor positive cells. Lepromatous macrophages from bacteriologically positive patients also demonstrated a low number of Con A positive cells. Data has also been presented to suggest that the alteration is induced by a soluble suppressor factor. The membrane changes observed in lepromatous macrophages may hence prevent the macrophages from reacting normally with their surroundings and especially the lymphocytes. This lack of interaction may further inhibit the lymphocyte from being activated and participating in the cascade of events involved in a cell-mediated immune reaction.