An indomethacin sensitive suppressor factor released by macrophages of leprosy patients

Reduction in F _c receptor expression as assayed by 'erythrocyte' rosetting of macrophage cultures from long term treated lepromatous leprosy patients (bactereologically negative) was seen in the presence of viable Mycobacterium leprae. Macrophages with and without intracellular bacilli demonstrated this reduction. On the basis of this observation the conditioned medium of Mycobacterium leprae infected macrophage cultures of lepromatous patients, were tested on macrophages from normal individuals for [³H]-leucine incorporation and antigen specific physical interaction with lymphocytes. Both these parameters showed decreased values as compared to the controls which were not exposed to this conditioned medium. Lymphocyte transformation to Mycobacterium leprae in leucocyte cultures of normal individuals was also reduced in the presence of the conditioned medium from lepromatous patients' macrophages. The indication that this factor may be a prostaglandin was suggested by the observation that its synthesis was inhibited by indomethacin. Its importance in the non-specific depression in cell-mediated immunity seen in lepromatous patients is discussed.