The CD34 molecule and hematopoietic progenitor cell studies--a challenge in clinical medicine.

The CD34 molecule, which is expressed at various levels on virtually all human hematopoietic progenitor cells (HPC), is a heavy glycosylated molecule with many different epitopes. A large series of CD34-specific monoclonal antibodies specific for different epitopes has been generated. Some of these antibodies do not react with particular HPC subpopulations. Thus, the antibodies used for HPC enumeration and isolation have to be carefully chosen with respect to what is aimed at.