The main cytokine, involved in erythema nodusum leprosum (ENL) reaction is:

Ans is 'c' i.e. Tumor necrosis factors (Ref: Harrison 16th/e p 968,969)Erythema nodosum leprosum or Type II lepra reaction occurs exclusively in patients near the lepromatous end of leprosy spectrum. In about 90% cases Erythema nodosum leprosum follows institution of chemotherapy. Immunopathology of Erythema Nodosum LeprosumENL is thought to be a consequence of immune complex reaction. Elevated levels of tumor necrosis factor (TNF) have been demonstrated in erythema nodosum leprosy.It is thought that TNF plays a central role in the pathobiology of this syndrome.