An improved immunomagnetic procedure for the isolation of highly purified human blood eosinophils

A simple method is described for the isolation of human peripheral blood eosinophils by an immunomagnetic procedure. Superparamagnetic particles were coupled to a monoclonal antibody against CD16, a molecule present on neutrophils but not on eosinophils. A peripheral blood granulocyte preparation, containing neutrophils and eosinophils, was incubated with these anti-CD16 particles. In the magnetic field of a permanent magnet, magnetically labelled neutrophils were then retained on columns with a ferromagnetic matrix. By this negative selection procedure, eosinophils of 99.5% purity were obtained from normal individuals and 99.6% purity from patients with eczema. A comparison was made between the immunomagnetic method and eosinophil isolation after N-formyl-methionyl-leucyl-phenyl-alanine treatment. Even in the case of individuals with very low eosinophil counts, the immunomagnetic method permits the efficient isolation of highly purified and functionally active eosinophils.