The CD nomenclature is established for a marker based on exchange of >2 mAbs to a set of labs throughout the world, verification of reactivity by serology and biochemistry, and longstanding use. SO the system of 'CD' actually transformed human immunology more than people who were not trying to do human immunology 25-30 years ago may realize. The problem over and over again with cellular approaches in my view is an overfocus on subsetting cells based on a marker without also trying to understand the function of the marker. Take 'CD4' for instance. We think we know so much about 'CD4 T cells', but what is CD4 doing on a subset of DCs and on some other myeloid cells. I could give you 20 more examples, e.g., CD5 B cells etc, CD34 is just another example.

Usually CD34 positive cells are stem/precursor cells from hematopetic system present in bone marrow and umbilical cord blood, also can be found on circulation depending on stimuli.

CD34 it is a marker that is very usufull in the bone marrow transplant field, since the CD34 cells number it is one of the paramenters used to predict the engraftment success .

Your question 'what is the function of CD34'? is very interesting, particularly since it may enable stem cells to bind to certain regions in the BM. CD34 is a phosphoprotein and thus clearly may regulate some key stem cell functions. But rather than get at the question of the function of a receptor, investigators, particularly in cellular immunology, prefer to simply use the CD molecule as a marker. Does anyone know if CD34 ligation changes the behavior of stem cells? If so, all the isolation of HSCs using anti-CD34 could be screwing them up!

The system of cluster of differentiation (CD) it is not a preference, it is a very useful system to universally identify an epitope. CD34 as I have said before it is expressed in early hematopoietic progenitor cells, but also in vascular progenitor endothelial cells.

However, few are actually known about the CD34 exactly function on these cells. I agree with Clark that it may regulate some key stem cell functions, maybe the stem state or its activation could be a signal for differentiation…

The CD nomenclature is established for a marker based on exchange of >2 mAbs to a set of labs throughout the world, verification of reactivity by serology and biochemistry, and longstanding use. SO the system of 'CD' actually transformed human immunology more than people who were not trying to do human immunology 25-30 years ago may realize. The problem over and over again with cellular approaches in my view is an overfocus on subsetting cells based on a marker without also trying to understand the function of the marker. Take 'CD4' for instance. We think we know so much about 'CD4 T cells', but what is CD4 doing on a subset of DCs and on some other myeloid cells. I could give you 20 more examples, e.g., CD5 B cells etc, CD34 is just another example.

I got it... You are right. Sometimes I get surprised by discovering that CDs are more promiscuous them I have imagined… and few are known about their function.

Does anybody know if fixation of bone marrow cells during intracellular staining could reduce or bleach the CD34 expression/staining?

Haifeng, are you refering to human or mouse BM cells? CD34 is NOT expressed on mouse stem cells, but on mouse stromal cells so if you are flushing the BM out of a femur, you may not even have postive cells in your culture, or very low quantity to start...CD150 may be a better marker. As far as fixation, check the Ab spec sheet to see if your CD34 Ab is compatible with fixed cells. One paper I read just washed the cells with PBS before staining. See attechement.

Thank you, Elizabeth. We are working on rhesus bone marrow cells. We routinely do fixation with BD cytofix/perm, which is good for all other markers, but not for CD34.

Haifeng, there some issues that should be checked for this stainig, have you looked at CD34 clone, in humans depending on the CD34 clone the staining it is not very good. Another issue that can be important is the fluorochrome, FITC is not appropriate for this staining, the best is using CD34 PE.

You are also permebilizing the cells with this product which allows you to stain for intracellular cytokines. Using this procedure for an epitope on cell surface is contraintuitive. The cell membrane is destroyed along with any membrane associated epitopes. Use a fixative without permabilization quailties such as acetone, methanol, formaldehyde.

refer to attached link for a good protocol

http://www.ihcworld.com/_protocols/general_ICC/staining.htm

Thank you, both Luciana and Elizabeth. Seems we need to try different ways to work this out.

We have developed a potent mouse monoclonal antibody to human CD34 protein backbone (3rd class epitope). The producing clone is 4H11 (APG). There are many researchers and companies using this antibody produced by this clone, also labeled by various fluorochromes. However the function of the CD34 glycoprotein is still unknown.