Selective stimulation by mouse spleen cell conditioned medium of human eosinophil colony formation

Stimulation of unfractionated or nonadherent human marrow cells in agar culture by pokeweed-mitogen-stimulated BALB/c mouse spleen cell conditioned medium (SCM) led, in most cultures, to the exclusive formation of eosinophil colonies. The culture system exhibited linearity of eosinophil colony formation with varying numbers of cells cultured, and the absolute numbers and size of SCM-stimulated eosinophil colonies approximated those in cultures stimulated by human placental conditioned medium. The active factor in SCM for human eosinophil colony formation was not clearly separable from the factors stimulating granulocyte-macrophage and eosinophil colony formation by mouse marrow cells on ammonium sulfate and phenyl boronate chromatography, but was of larger size than the mouse-active factors and separable from them by phenyl sepharose chromatography. This selective culture system for eosinophil colony formation should be of value for studies on human eosinophil progenitor and maturing cell populations in a variety of disease states.