Gene knock-in mice having a targeted insertion of the human diphtheria toxin receptor within the eosinophil peroxidase locus are described. Administering diphtheria toxin to such animals results in the loss of eosinophils in the animal. Accordingly, the knock-in mice and nucleic acid constructs featured in the document can be used to generate eosinophil-deficient transgenic animals that are useful for studying pathologies and treatments relating to tissues and organ systems that typically contain eosinophils.
