Defective blood mononuclear phagocyte function in patients with leprosy.

Patients with lepromatous leprosy possess a defective lymphocyte function in vivo and in vitro that is less evident in the tuberculoid form. Data concerning their macrophage ability to digest Mycobacterium leprae are controversial. The purpose of this study was to determine whether monocytes from patients with either tuberculoid or lepromatous leprosy were altered in their enzyme systems, that is myeloperoxidase-dependent and myeloperoxidase-independent systems. The ability of adherent blood monocytes to ingest and kill Candida pseudotropicalis after 30 and 60 min of incubation with yeast cells was tested. Mononuclear phagocytic cells from patients with either principal form of leprosy functioned similarly to normal monocytes in phagocytosis while their fungicidal activity for C. pseudotropicalis was statistically significantly altered and was more evident in the lepromatous than in the tuberculoid type. The results indicate that peripheral blood monocytes from patients with leprosy possess an impaired enzymatic candidacidal activity.