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. Cells forming eosinophil colonies (EO-CFC) are present in normal bone marrow and differ in many respects from the granulocyte-monocyte-forming cell (GM-CFC) (Dao et al., 1977a,b; Inoue & Ottenbreit, 1978). Although GM-CFC are greatly concentrated in the null cell subset of peripheral blood lymphocytes (Richman et al., 1978), it is not known whether EO-CFC are also null cells. We have investigated EO-CFC in normal human bone marrow and peripheral blood, utilizing cell segregation prior to soft agar culture to specifically characterize EO-CFC surface markers and growth characteristics. Our results indicate that the EO-CFC is concentrated in the null cell lymphocyte subset and bears the HLA-DR(+) marker.