Interleukin-1 released by blood-monocyte-derived macrophages from patients with leprosy.

In highly purified blood-monocyte-derived macrophages collected from patients with leprosy and from healthy individuals and cultured in vitro with mycobacterial antigens such as Mycobacterium bovis BCG or Mycobacterium leprae, we nonspecifically induced the synthesis of interleukin-1. Normally, all supernatants from cultured macrophages of all subjects tested produced similar amounts of interleukin-1. However, only in patients with lepromatous leprosy, M. leprae, but not BCG, induced high-level synthesis of prostaglandin E2, which acted as a suppressor factor in the mouse thymocyte proliferative assay used to measure the interleukin-1 content of the supernatants. Normal interleukin-1 content of those supernatants was demonstrated by blocking the prostaglandin E2 synthesis by the addition of indomethacin to the medium throughout the experimental procedure. We also tested the efficiency of a combination of BCG and M. leprae in reducing the prostaglandin E2 synthesis, but with the methodology used, we did not observe any beneficial effect of such a combination. These results demonstrate the possible role of M. leprae in the induction of at least one of the suppressive monokines and are additional arguments for the involvement of macrophages in the suppression of the specific cell-mediated immunity to M. leprae observed in lepromatous leprosy.