Activation of complement by Mycobacterium leprae requires disruption of the bacilli.

Objective: The immune-mediated events that precipitate erythema nodosum leprosum (ENL) are not well understood. One component may be the complexing of antibody with antigens released from infected macrophages, the activation of complement and the subsequent local inflammation. We assess here the ability of highly-purified, disrupted M. leprae, to activate complement.
Results: Intact and sonically-disrupted crude and alkali-purified nu/nu mouse-derived M. leprae suspensions were incubated with normal serum and a hemolytic titer (CH50) was determined as a measure of complement fixation. Crude M. leprae consumed complement, and disrupted preparations more than the intact. Purified M. leprae preparations did not consume complement unless disrupted.
Conclusion: M. leprae, if disrupted, can activate complement. This supports a hypothesis that links released antigens with ENL, and may explain the increased probability of an occurrence of ENL following chemotherapy.