Studies appearing in 1996 reported that AHR to methacholine and lung eosinophilia in C57BL/6 mice were markedly attenuated by targeted deletion of the IL-5 gene (9); in contrast, monoclonal antibodies blocking IL-4, but not those blocking IL-5, attenuated AHR in OVA-sensitized and -challenged BALB/c mice (10), even though anti–IL-5 effectively blocked airway eosinophilia. This evidence concerns the gene IL5 and medical procedure.