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 bas ophils from whole blood of normal subjects to at least 95% purity. Bas ophils are separated from other cell types dy density-dependent sedime ntation in Percoll and cell sorting, based solely on their size and gr anularity. The mean overall yield ranged from 5% to 28%. The procedure is typically completed within 4 h. The highly purified basophils obta ined are functionally competent and morphologically intact. They relea se histamine in response to Fc epsilon RI-mediated stimulation, expres s Fc epsilon RI and BSP-I ligand as analyzed by flow cytometry, and ex hibit the known characteristic ultrastructural features of basophils b y electron microscopy. This procedure avoids positive-selection antibo dies that might perturb receptors on basophils or negative-selection a ntibodies that might activate other cell types, and can be used to obt ain basophils for studies in vitro.