Helper T-cell subsets in mouse leishmaniasis: induction, expansion and effector function

It has been a surprise to find that the two distinct subsets of mouse CD4+ T cells identified from clones cultured in vitro also occur during Leishmania infection. The spectrum of disease encountered during these infections ranges from successful resolution to fatal dissemination and in mice these outcomes are accompanied by expansion of TH1 or TH2 CD4+ cells, respectively. This review focuses on the mechanisms that cause such disparate responses to the parasite.