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Hématologie

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Mast cells and mastocytosis Volume 5, issue 5, Septembre - Octobre 1999

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Mast cells derive from multipotent hematopoietic stem cells but terminate their differentiation in tissues. These cells are very heterogeneous, not only with respect to their tissue location and structure, but also at the functional and histochemical levels, a fact that explains the complexity of studies performed on these elements. Our knowledge on the factors responsible for mast cell differentiation from hematopoietic stem cells have been considerably enriched these last years with the discovery of a great number of cytokines that are involved in this differentiation process, especially in the mouse. In addition to the well characterized function of mast cells as mediators of the immediate hypersensitivity, it has been shown recently that mast cells possess two major physiological properties as antigen presenting cells, and as important partners in the anti-infectious defense of the organism. Mast cells are also the targets of rare proliferative disorders named systemic mastocytosis, very heterogeneous in their biological and clinical presentations. Systemic mastocytosis are characterized by an uncontrolled proliferation of mast cells disseminated in many tissues, especially in the bone marrow, which links these disorders to the myeloproliferative syndromes. Although the initial events leading to these diseases are not yet unraveled, alterations of the stem cell factor or more frequently its membrane receptor c-Kit, have been described. Particularly interesting are punctual mutations which result in a constitutively activated receptor. In some cases, systemic mastocytosis have been successfully treated by antiproliferative molecules, particularly interferon, but these molecules do not target specifically the intrinsic defect involved in this pathology. For these reasons, therapeutic strategies are envisaged that will specifically target the abnormal proliferative signal triggered by the activated c-Kit.