Selective upregulation of a functional beta(7) integrin on differentiating eosinophils

Background: The sequence of adhesion-molecule expression during eosinophil differentiation remains unclear. Methods: We analyzed the surface expression of alpha(4), beta(1), and beta(7) integrins and compared it to established myeloid developmental markers, using the eosinophilic cell line HL-60 clone 15, as well as cord and peripheral blood differentiation assays. Results: Cells induced to eosinophil differentiation by treatment with butyric acid, IL-5, and GM-CSF showed a significant upregulation of beta(7) integrin expression coincident with a marked upregulation of CD35 and attenuation of CD33 and beta(1) integrin expression. In addition, adhesion of induced HL-60 clone 15 cells to fibronectin was attenuated by a beta(7) integrin antibody. Conclusions: Our data show that protein synthesis-dependent upregulation of the functional beta(7) integrin occurs under conditions when alpha(4) and beta(1) integrins are fully expressed, indicating a sequential appearance of specific adhesion molecules on differentiating eosinophil progenitors.