Comparative analysis of class I, II and III epitope-detecting CD34 monoclonal antibodies by quantitative flow cytometry

The aim of this study was to compare different CD34 monoclonal antibodies ( MAbs) belonging to three different classes: MY10 class I, QBend10 class II, a mixture of three selected MAbs class I and II designated as CD34 Pool, a nd 8G12 class III. Bone marrow (BM) samples from 13 healthy donors were ana lyzed for: 1) percentage of CD34+ cells, 2) quantitative expression of CD34 epitopes (antigen's density - AgD) using a quantitative indirect immunoflu orescence (QIFI) test, 3) study of CD34+ cell subsets defined by CD34 and C D38 coexpression. 8G12 MAb showed the highest reactivity with regard to the percentage of detected CD34+ cells and Ago on these cells. A nearly identi cal percentage of CD34+ cells was detected with CD34 Pool, but with a lower Ago. With QBend10, the percentage of CD34 expressing cells was insignifica ntly decreased and the Ago was slightly lower. The expression of the MY10 e pitope was the lowest and was detected on the lowest number of CD34+ cells. Concerning CD34 and CD38 coexpressing subset, we observed that 8G12 class III MAb detected CD34(lo)CD38(dim) cells with comparable efficiency with MY 10 class I MAb, but with significantly higher level than QBend10 class II a nd CD34 Pool class I+II MAbs. The CD34(hi)CD38(dim) subset was detected wit h the same efficiency by QBend10, CD34 Pool or 8G12 MAbs but with significa ntly higher frequency than MY10 MAb. In conclusion: class II and III MAbs appear preferable for flow cytometric quantification of CD34+ cells; for CD34+ cell subsets determination class I II MAbs should be suitable.