Flow cytometric analysis of mast cells from normal and pathological human bone marrow samples: identification and enumeration.

In the present paper we have used a three-color immunofluorescence procedure combined with flow cytometry cell analysis and sorting for the identification and enumeration of human mast cells in both normal and pathological bone marrow samples. Our results show that bone marrow mast cells are clearly identifiable on the basis of their light-scatter properties and strong CD117 expression. These cells were negative for the CD34, CD38, and BB4 antigens. In addition, they were CD33+ and displayed a high reactivity for the anti-IgE monoclonal antibody. The identity of the CD117-strong+ cells (mast cells) was confirmed by both microscopic examination and flow cytometry analysis. The overall frequency of mast cells in the bone marrow samples analyzed in the present study was constantly lower than 1%. The lowest frequencies corresponded to normal human bone marrow samples (0.0080 +/- 0.0082%) and the highest to those patients suffering from indolent systemic mast cell disease (0.40 +/- 0.13%). In summary, our results show that the identification and enumeration of bone marrow mast cells can be achieved using multiparametric flow cytometry. Moreover, once identified, mast cells are suitable for being characterized from the phenotypic and the functional point of view, facilitating the comparison between normal and abnormal mast cells.