Patients with lepromatous leprosy are unresponsive to lepromin skin-test material and possess defective lymphocyte function in vitro, including impaired mitogenesis in response to antigens of Mycobacterium leprae. It has been claimed that their macrophages cannot digest M. leprae in vitro; such a defect could explain both lepromin nonreactivity and impaired lymphocyte function on the basis of failure of the afferent limb of the immune response (i.e., defective macrophage "processing" of M. leprae). The present studies indicate that macrophages from patients with lepromatous and tuberculoid leprosy and from normal donors do not differ in their ability to digest heat-killed M. leprae in vitro, or in their ability to sustain the viability of M. leprae in tissue culture; that monocytes, macrophages, and polymorphonuclear leukocytes of leprosy patients and controls possess equivalent microbicidal activity against Listeria monocytogenes, Escherichia coli, Proteus vulgaris, Staphylococcus aureus, and Candida albicans; and that polymorphonuclear leukocytes from patients with lepromatous leprosy iodinate ingested bacteria normally. Whether the basic immune defect leading to the development of lepromatous leprosy resides in the lymphocyte or in the macrophage remains to be determined. However, the present study shows that phagocytic cells from patients with either principal form of leprosy function normally in a variety of sophisticated tests of antimicrobial function.
D J Drutz, M J Cline, L Levy