[Leishmaniasis: effect of factors present in serum].

An important role in the interaction between protozoan parasite Leishmania and host is determined by serum factors. The activation of complement can have resistance-promoting effects (due to the lysis of parasite) or disease-promoting effect (due to the opsonization of Leishmania). Also lymphokines can determine resolution or progression of the infection. Particularly, gamma-interferon "in vitro" increases the killing of the parasite and "in vivo" cures cutaneous leishmaniasis.