[5] The protein encoded by this gene is the predominant constituent of the crystalline core of the eosinophil granule.

This protein may be involved in antiparasitic defense mechanisms as a cytotoxin and helmintho-toxin, and in immune hypersensitivity reactions.

It is directly implicated in epithelial cell damage, exfoliation, and bronchospasm in allergic diseases.

It is a potent enzyme against helminths and is toxic towards bacteria and mammalian cells in vitro.

The eosinophil major basic protein also causes the release of histamine from mast cells and basophils, and activates neutrophils and alveolar macrophages.