Interleukin 2 distinctly activates human basophils in skin disorders

Basophils are important effector cells in allergic inflammation, anti-parasitic immune response and skin disorders. A number of activators including interleukin 3 (IL-3) and IgE have been identified in the regulation of human basophils expressing mediators such as histamine and leukotriene C4 (LTC4) and cytokines, including IL-4 and IL-13. Human basophils express high levels of IL-2 receptors. However, the function of the IL-2 pathway in basophils remains unknown. Here, we identify that IL-2-stimulated human basophils in vitro express a variety of inflammatory cytokines and chemokines including IL-5, IL-13, GM-CSF and CCL-17. Of note, one of the top regulated cytokines, IL-5, was for the first time identified to be expressed in human basophils and was distinctly regulated by IL-2, independently of IL-3 and IgE. Immunofluorescence analysis of skin specimens from bullous pemphigoid and eczema revealed that infiltrating basophils in skin lesions widely express IL-5 and GM-CSF. Together, our findings reveal IL-2 as a novel regulator of human basophils to express IL-5 and GM-CSF in skin disorders. This adds a new layer to support the importance of basophils in skin disorders. Human basophils were pre-enriched from PBMCs from buffy coat by Magnetic-activated cell sorting (MACS) positive sorting using rat anti-human CRTH2 microbeads. Next, basophils were further purified by FACS sorting of FSClowSSClowCD4-CRTH2high populations.Purified basophils at a density of 2×105 cells/well in a 96-well plate were cultured either with or without human IL-2 (10 ng/mL) (n = 3) (10 ng/mL) for 24 hours. Gene expression microarray analysis was performed using SurePrint G3 Human Gene Expression 8×60K V2 microarray according to the manufacture’s instruction.