IL4 and cutaneous leishmaniasis: Experimental cutaneous leishmaniasis in genetically inbred mice was the first model which showed a mouse strain-dependent polarization of IL-4 and IFN-γ production by CD4+ T cells correlating with either disease susceptibility or resistance (Heinzel et al., 1989) and therefore formed the basis of the Th1 and Th2 paradigm (Mosmann and Coffman, 1989).