FcɛRI cross-linking and IL-3 protect human basophils from intrinsic apoptotic stress

The relevance of key antiapoptotic Bcl-2 family members in primary human basophils was evaluated by using small-molecule inhibitors termed Bcl-2 homology domain 3 (BH3) mimetics, which specifically inhibit Bcl-2 (ABT-199/venetoclax [Venclaxta]), myeloid cell leukemia 1 (Mcl-1; A-1210477), or Bcl-2 and B-cell lymphoma–extra large (Bcl-xL; ABT-263/navitoclax).3,4 Because all 3 types of granulocytes are developmentally related but differ in their expression profiles of Bcl-2 family members (see Fig E1, A, and the Methods section in this article's Online Repository at www.jacionline.org), eosinophils and neutrophils were used as comparisons. [...]eosinophil survival was reduced by 50% in response to 28 nmol/L ABT-263 (see Fig E2, A). [...]we assumed that in the absence of proapoptotic stimuli, the effect of autocrine IL-3 signaling on cell viability is marginal because of the high constitutive expression of Bcl-2 and its consequential low rate of spontaneous cell death within this timeframe. Annexin/PI staining was performed according to the manufacturer's instructions. Since eosinophils exhibit strong auto-fluorescence in the fluorescein isothiocyanate (FITC)-channel, Annexin-V allophycocyanin (APC) was used for this particular cell type, whereas basophils and neutrophils were stained with Annexin-V FITC.