COULTER Stem-Trol Control Cells are preserved KG-1a cells, that have been modified and stabilized (patent pending) to express the CD34 Class III epitopes and the CD45 leucocyte common antigen at densities that approximate normal human hematopoietic progenitor cells (HPC). This product is a ready-to-use cell suspension. COULTER Stem-Trol Control Cells provide an antibody-to-antigen positive control for CD34 and CD45 staining in flow cytometry studies. The concentration of this cell suspension is precisely calibrated. Therefore it is also designed as an internal control for absolute count verification procedures in CD34+ HPC absolute counting process.