Phenotypic analysis of human basophils in blood and inflamed mucosal tissues. (A-B) Phenotype of human basophils analyzed in relation to FcϵRI and SIRP-α expression in whole blood lysate. (A) FcϵRI^highSIRP-α^low cells were characterized as HLA-DR⁻CD123⁺CD1c⁻CRTH2⁺c-kit⁻CD203c⁺ (red), FcϵRI^lowSIRP-α^high cells are identified as CRTH2⁻CD1c⁺ (green), and HLA-DR⁺CD123⁺ cells as c-kit⁻CD203c⁻ (blue; B). HLA-DR⁻CD123⁺ and FcϵRI^highSIRP-α^low cells are shown by forward and side-scatter parameters. Correlation between frequencies of FcϵRI^high SIRP-α^low cells and HLA-DR⁻CD123⁺ cells (n = 11) is shown. (C) Morphologic studies of the purified FcϵRI⁺ cell subsets using Wright staining. (D) FACS-sorted basophils or CD1c⁺ DCs were stimulated in the presence or absence of IL-3 (10 ng/mL) with or without IL-33 (10 ng/mL). Histamine release was measured by ELISA after 24 hours. The mean ± SEM for 5 donors is shown. ND indicates not detectable. (E-F) Single-cell suspensions were prepared from the lungs of patients undergoing lung transplantation (E) or the colons of IBD patients (F). Basophils were identified as FcϵRI^highSIRP-α^lowc-kit⁻ cells coexpressing CD123 and CRTH2. Forward and side-scatter plot and HLA-DR expression on basophils (c-kit⁻CRTH2⁺ or c-kit⁻CD123⁺ cells) and mast cells (c-kit⁺CRTH2⁻ or c-kit⁺CD123⁻ cells) are examined. Data are representative of 3 CF, 1 bronchiectasis (BE), 3 CD, and 3 UC patients.