In vitro and in vivo effects of interleukin 2 on the protozoan parasite leishmania

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Abstract
T cells can have either resistance-promoting or disease-promoting effects in murine cutaneous leishmaniasis. It is known that the adoptive transfer of parasite-specific helper T cells led to an exacerbation of Leishmania-induced lesions. This work presents evidence that lymphokines produced by activated T cells could be involved in this exacerbating process by directly stimulating the parasite growth. In the presence of activated T cell supernatants, the in vitro growth of Leishmania mexicana amazonensis promastigotes was greatly enhanced. This effect was reproduced by addition of recombinant interleukin 2 (IL 2). An anti-IL 2 antibody partially reversed the stimulatory effect of IL. An in vivo in situ treatment of infected mice with IL 2 led to an exacerbation of the lesions. The increase in footpad swelling after IL 2 treatment was correlated with a higher number of parasites per lesion. The protective effect of cyclosporin A against the development of Leishmania infection was abolished by IL 2 treatment. As we observed that IL 2 has a stimulatory effect on the in vitro Leishmania growth, we speculate that exacerbation of the lesions observed in vivo after IL 2 treatment could be partially related with a direct effect of IL 2 on the parasite growth.