Immunophenotypic analysis of human mast cells by flow cytometry

The immunophenotypic identification and enumeration of human bone marrow mast cells represents a clear demonstration of the utility of flow cytometry for rare-event analysis. The basic approach can be applied to a variety of specimens, including bone marrow, peripheral blood, ascitic fluid, and lymphoid tissue such as adenoids. Special emphasis is placed on markers with potential utility for distinguishing between normal, reactive, and pathological mast cells. From the clinical aspect, immunophenotypic analysis of mast cells may have great utility in supporting the diagnosis of tissue involvement in mastocytosis.

Expression of high amounts of the CD117 molecule in a case of B-cell non-Hodgkin's lymphoma carrying the t(14:18) translocation

The c-kit proto-oncogen (CD117) has been described to be present in normal and neoplastic hemopoietic cells including both myeloid and lymphoid lineages. Among the normal lymphoid cells CD117 expression would be restricted to a small subset of NK-cells, and to early T-cell precursors and it is not expressed by normal B-cells. Regarding chronic lymphoproliferative disorders the only data provided up to now suggests that CD117 expression is restricted to cases of Hodgkin's disease and anaplastic large-cell lymphoma. In the present paper we describe a case of a B-cell chronic lymphoproliferative disorder carrying the t(14:18) translocation as demonstrated by molecular studies, in which the flow cytometric immunophenotypic analysis of both peripheral blood and bone marrow samples revealed the expression of high amounts of the CD117 antigen in the surface of the clonal B-cell population. Further studies are necessary to explore both the functional role of c-kit expression in the neoplastic B-cells from this patient and its potential utility for the diagnosis and follow-up of patients with B-cell non-Hodgkin's lymphoma.

Human bone marrow mast cells from indolent systemic mast cell disease constitutively express increased amounts of the CD63 protein on their surface

The quantitative measurement of the expression of both cytoplasmic and surface CD63 antigen by human mast cells from both normal and pathological bone marrow samples was studied by use of flow cytometry. Our major goal was to analyze whether in vivo CD63 expression by human bone marrow mast cells could be useful to discriminate bone marrow mast cells from patients with mastocytosis from other conditions. For that purpose, a total of 65 subjects corresponding to 12 healthy volunteers, 25 B-cell chronic lymphoproliferative disorders, 5 reactive bone marrow samples, 4 myelodysplastic syndromes, and 19 mastocytosis were analyzed. The expression of both surface and cytoplasmic CD63 by human bone marrow mast cells is clearly demonstrated. Our results show that high amounts of CD63 are present in human bone marrow mast cells most of it corresponding to an intracellular localization. No significant differences in CD63 expression were observed as regards both total and cytoplasmic CD63, except for higher CD63 levels in adult patients with mastocytosis (P = 0.05). By contrast, the mean level of surface CD63 significantly varied between the different groups of individuals. Accordingly, patients with monoclonal gammopathies displayed a slight decrease (P = 0.1) in surface CD63 expression, whereas bone marrow mast cells from adults with indolent systemic mast cell disease showed significantly (P = 0.0005) higher levels of surface CD63 as compared to healthy controls.