Figure 5.

The mechanism of the leprosy reaction. (a) T1 R is led by a cellular immune response mediated via CD4+ T cells. Activated macrophages release pro-inflammatory Th1 cytokines, such as IFN-γ, TNF-α, IL-1β, IL-6, IL-2, IL-12, TGF-β and iNOS, which cause tissue damage. (b) ENL is a generalized proinflammatory reaction featuring the infiltration of neutrophils. The activation of complement, immune complexes, increasing CD4+/CD8+ T cell subset ratios and high degree of proinflammatory cytokines including TNF-α in the lesions and in the circulation can also be observed. ENL shows low cellular immunity, but there are enough B cells and plasma cells to produce antibodies against M. leprae. In the acute stage of ENL lesions, a large number of neutrophilic infiltrations is observed. An activated CD8+ T cell secretes cytotoxic granule proteins such as perforin and granzymes which lead to apoptosis of the cells.