Accelerated clearance of Onchocerca microfilariae and resistance to reinfection in lnterleukin‐4 gene knockout mice

Immunity to Onchocerca microfilariae (mf) in mice is associated with CD4+ Th2 cells and is dependent on IL‐5. In view of the role ofIL‐4 in the development of Th2 cells, we have utilized IL‐4 gene knockout mice (IL‐4‐1‐) to investigate microfilarial clearance and resistance to reinfection. Paradoxically, in the absence of IL‐4 there is accelerated clearance of microfilariae during a primary infection and unimpeded expression of resistance to reinfection. IL‐4‐1‐ mice showed a lack of an IgE response although peripheral eosinophilia was equivalent to wildtype controls. The data presented here suggest that elimination ofmfcan occur independent of IL‐4 and that in this model it may even be detrimental to the host.