Basophil Granulocytes
Basophil granulocytes develop in the bone marrow and are released into the circulation as mature end-stage cells representing less than 1% of blood leukocytes.
Basophils play a critical role in allergic disease by infiltrating sites of allergic inflammation and releasing mediators and cytokines that perpetuate type I (immediate) hypersensitivity reactions.
Elevated basophil counts (basophilia) can be due to myeloproliferative disorders like Chronic myeologenous leukemia (CML)
Reduced basophil numbers can be due to acute inflammation, infection and acute allergic reactions.
(Sources: Kubo, 2017; MedicineNet)