IL4 and infection: However, considering that the impact of IL-4-mediated DC instruction was most pronounced in the susceptible BALB/c background in response to more virulent and less virulent strains of parasites, the role of early IL-4 signaling on keratinocytes needs to be investigated on a nonhealer BALB/c genetic background during cutaneous leishmaniasis to fully elucidate effector immune responses in response to infection with more virulent and less virulent L. major strains.