Basophils: Understanding Their Role in the Immune System

Basophils (<1% leukocytes) are granulocytes with high-affinity IgE receptors (FcεRI). Key roles:

• Allergic Effector: Cross-linking of IgE by allergen → degranulation → histamine, leukotrienes, prostaglandins → vasodilation, bronchoconstriction, mucus, pruritus (early phase).
• Late Phase: IL-4, IL-13 recruit eosinophils, Th2 cells.
• Parasite Defense: IL-4/IL-13 promote IgE class switching, eosinophilia, gut expulsion.
• Immunomodulation: Regulate dendritic cells, T cells, B cells.
• Autoimmunity: Implicated in lupus, chronic urticaria.

Clinical Relevance

• Basophilia: Chronic myeloid leukemia, polycythemia vera, hypothyroidism, IBD.
• Basopenia: Acute allergic reaction (sequestration), stress, corticosteroids.
• Basophil activation test (BAT): Functional assay for allergy diagnosis.