Dear Beth, We too have seen what we strongly suspect to be eosinophils staining with anti-CD34 conjugates (class III HPCA2 PE). In our case it was from atopic individuals whose blood contains elevated levels of CD34+ cells. 'Normal' CD34+ cell in peripheral blood form a discrete cluster on CD45 vs side scatter analysis (see ISHAGE Guidelines for CD34+ cell Enumeration, J. Hematotherapy 5:227-236, 1996). Symptomatic atopic individuals generally exhibit increased numbers of these cells but the cluster tends to form a continuous 'comet-tail' towards increased side scatter and CD45 expression. These cells exhibit the light scatter characteristics that you described for your 'mystery population'. In the PB of asymptomatic atopic individuals, we often see an increase in basophil/eosinophil progenitors (American Journal of Respiratory Cell and Molecular Biology 15: 645-654, 1996.) Although beyond topic, we have also seen CD34+ basophils in transient leukemias of newborn Down Syndrome samples and more commonly in marrow samples from CML patients. Finally (and even further beyond topic), we have seen a marrow (from what turned out to be an MDS patient) that contained nearly 15% CD34+ cells, half of which exhibited distinctly granular cytoplasm by fluorescence microscopy. Many of these cells formed a 'comet tail' on CD45 versus side scatter but in this case they virtually overlapped the neutrophil population. Aren't annecdotes wonderful? Rob Sutherland
This archive was generated by hypermail 2b29 : Wed Apr 03 2002 - 11:50:00 EST