IL-13 released by and localized in human basophils

Area of Science:

• Immunology
• Cell Biology
• Allergy Research

Background:

• Human basophils are known producers of IL-4.
• IL-13, a cytokine structurally similar to IL-4, had not been previously identified as a basophil product.

Purpose of the Study:

• To investigate and demonstrate the production of IL-13 by human basophils.
• To characterize the conditions and kinetics of IL-13 release from basophils.

Main Methods:

• Immunocytochemistry and electron microscopy were used to localize IL-13 within basophils.
• Enzyme-linked immunosorbent assay (ELISA) quantified IL-13 secretion into culture supernatants.
• Stimulation of basophils and other immune cells (PBMC, neutrophils, eosinophils) with various agents (anti-IgE, anti-FcepsilonRIalpha, IL-3, A23187, PHA, PMA, IL-5) was performed.

Main Results:

• Approximately 70% of anti-FcepsilonRIalpha-stimulated basophils stained positive for IL-13, localized to basophilic granules.
• IL-13 secretion was detected as early as 3 hours post-stimulation, increasing up to 24 hours, with distinct kinetics from histamine and IL-4 release.
• Basophils, but not mononuclear cells, neutrophils, or eosinophils, produced IL-13 upon stimulation with anti-IgE or anti-FcepsilonRIalpha; IL-3 enhanced this production.
• Peripheral blood mononuclear cells (PBMC) produced IL-13 upon PHA stimulation, but not with A23187/PMA.

Conclusions:

• This study provides the first evidence of IL-13 production by human basophils.
• Basophils are identified as a significant source of proallergic cytokines, in addition to their known mediator release functions.
• These findings highlight the expanded role of basophils in allergic inflammation and immune responses.