CD34 is the most commonly used marker for “hematopoietic stem/ progenitor cells” in clinical hematology. Clinicians even use this marker as a quality criteria for the hematopoietic graft. In reality, however, number of CD34 is not always correlate with good lineages engraftment and outcome. Apparently, CD34 is not good marker for human hematopoietic stem cells (HSC), but acceptable for some committed progenitors. Therefore, despite the common assumption, CD34 is a surrogate marker for HSC and progenitors. Recently, I came across of excellent critical review about CD34 and its utility in clinical HSC transplantation.
One of the “first rate” parameters in clinical transplantations in hematology; i.e. the CD34+ positive cell dose, has been discussed with respect to the functional heterogeneity and variability of cell populations endowed by expression of CD34. This parameter is useful only if the relative proportion of stem and progenitor cells in the CD34+ cell population is more or less maintained in a series of patients or donors. This proportion could vary with respect to the source, pathology, treatment, processing procedure, the graft ex vivo treatment and so on.
“Stem cell” label for CD34+ cells as misconception:
Furthermore, most clinicians and biologists who are not directly involved in stem cell research have a tendency to add the term “stem cells” each time they say or write “CD34+”. This tendency has been a permanent source of misunderstanding and confusion and it heavily affects experimental and clinical hematology.
The author made a conclusion:
In addition, to avoid further confusion, the CD34+ cells should not be named “stem cells” or “progenitor cells” since these denominations only concern functionally characterized cell entities.
Very interesting review. Highly recommended!