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

Unlabelled: 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, and 8G12 class III. Bone marrow (BM) samples from 13 healthy donors were analyzed for: 1) percentage of CD34+ cells, 2) quantitative expression of CD34 epitopes (antigen's density - AgD) using a quantitative indirect immunofluorescence (QIFI) test, 3) study of CD34+ cell subsets defined by CD34 and CD38 coexpression. 8G12 MAb showed the highest reactivity with regard to the percentage of detected CD34+ cells and AgD on these cells. A nearly identical percentage of CD34+ cells was detected with CD34 Pool, but with a lower AgD. With QBend10, the percentage of CD34 expressing cells was insignificantly decreased and the AgD was slightly lower. The expression of the MY10 epitope 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 CD34loCD38dim cells with comparable efficiency with MY10 class I MAb, but with significantly higher level than QBend10 class II and CD34 Pool class I+II MAbs. The CD34hiCD38dim subset was detected with the same efficiency by QBend10, CD34 Pool or 8G12 MAbs but with significantly 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 III MAbs should be suitable.