Purification of human basophils by density and size alone

Basophils typically account for approximately 1% of the white cells in peripheral blood. We have developed a unique method for purifying basophils from whole blood of normal subjects to at least 95% purity. Basophils are separated from other cell types by density-dependent sedimentation in Percoll and cell sorting, based solely on their size and granularity. The mean overall yield ranged from 5% to 28%. The procedure is typically completed within 4 h. The highly purified basophils obtained are functionally competent and morphologically intact. They release histamine in response to Fc epsilon RI-mediated stimulation, express Fc epsilon RI and BSP-1 ligand as analyzed by flow cytometry, and exhibit the known characteristic ultrastructural features of basophils by electron microscopy. This procedure avoids positive-selection antibodies that might perturb receptors on basophils or negative-selection antibodies that might activate other cell types, and can be used to obtain basophils for studies in vitro.