Membrane marker characterization of the eosinophil colony-forming cell

We investigated the membrane markers of the eosinophil colony-forming cell (EO-CFC). Eosinophil colonies were identified by their ability to show densely packed cell growth and by staining for cyanide-resistant peroxidase activity. Bone marrow cells were characterized prior to soft agar culture by one of two methods: (1) standard erythrocyte (E) and erythrocyte-antibody-complement (EAC) rosetting, or (2) by the human T- and B-cell surface markers, Leu 1 and HLA-DR, using the fluorescence-activated cell sorter. Eosinophil colonies developed mainly from the nonrosetting, null cell population. EO-CFC lacked the human T-cell marker Leu 1, but demonstrated the human B-cell marker, HLA-DR. EO-CFC were also present in peripheral blood and possessed similar properties to those in the bone marrow. The results indicate that EO-CFC are derived from the null lymphocyte cell population and possess HLA-DR markers.