In vitro activation of neutrophils by suspensions of Mycobacterium leprae.

Activation, defined as an increase in the proportion of cells that reduce nitroblue-tetrazolium in vitro, is present in neutrophils from patients with reactional lepromatous leprosy but not in neutrophils from patients with non-reactional lepromatous leprosy. Neutrophils from patients with all forms of leprosy are equally well activated by endotoxin in vitro. We have now shown that in vitro activation induced by Mycobacterium leprae suspensions is of comparable magnitude in neutrophils from patients with all forms of leprosy (including lepromatous and reactional lepromatous leprosy). There is no intrinsic neutrophil anergy in patients with lepromatous leprosy vis-à-vis M. leprae as pertains to activation. Spontaneous activation in reactional lepromatous leprosy is likely due to an indirect mechanism, probably of immunologic nature, and not simply to the presence of circulating Mycobacterium leprae in the blood.