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We describe a patient with fever and multiple osteolytic bone lesions accompanied by hypercalcemia, a duodenal ulcer, anemia, and thrombocytopenia. Bone marrow showed a dense infiltration by abnormal cells characterized by small basophil granula, erythrophagocytosis and nuclear atypia. These cells were positive for toluidine blue and partly for myeloperoxidase and chloroacetate esterase, expressed myeloid differentiation markers, and exhibited multiple numerical and structural chromosome aberrations. Molecular genetic analysis showed no breakpoint cluster region rearrangement. Electron microscopy demonstrated granula both of basophil and mast cell type. Concluding, in this patient an acute hematopoietic malignancy with many features of malignant mastocytosis but also with signs of a basophil differentiation. This is further support for a hematopoietic stem cell origin of human mast cells.

Surgical human thymus, upper respiratory tract, lung and small and large bowel specimens were analyzed for the presence of interleukin 2 receptor (IL2-R)-positive cells. Histochemical (toluidine) and immunologic (anti-IL2-R monoclonal antibody) staining procedures revealed a distinct anti-IL2-R positivity in most of metachromatically staining cells. These positive cells were observed not only in tissues showing strong inflammatory reaction and mast cell hyperplasia, as in Crohn's disease, but also in those not histologically affected by pathologic conditions. This finding suggested that human mast cells, like T blast cells, express the p55 chain of IL2-R on their surface. To see whether IL2-R was being actively synthesized, a cell preparation rich in peripheral blood basophils (PBB), which are cells closely related to mast cells, was obtained. Ultrastructural analysis of PBB after indirect immunogold procedure revealed that the vast majority expressed the IL2-R. Moreover, the presence of intracellular reaction products in the cytoplasm of most membrane-positive PBB was indicative of active antigen synthesis. Furthermore, Northern blot analysis evidenced specific IL2-R mRNA in PBB, while its expression was augmented several times when PBB were cultured in the presence of stimulated T cell supernatant.

Human eosinophils contain several distinctive proteins including eosinophil granule MBP and the membrane-associated CLC protein (lysophospholipase). Human basophils also contain these proteins, indicating biochemical similarities between eosinophils and basophils. To determine whether MBP or CLC protein is present in connective tissue mast cells, we studied human lung and cutaneous mast cells by immunofluorescence by utilizing specific antibodies to CLC and MBP. Cytocentrifuge slides of enriched lung mast cells and mast cells in sections of formalin-fixed, paraffin-embedded cutaneous tissue from urticaria pigmentosa lesions were stained for CLC and MBP. Neither pulmonary nor cutaneous mast cells stained for CLC protein or MBP. In contrast, lung and cutaneous eosinophils in the same preparations showed bright staining for both proteins. The failure to find CLC protein and MBP in mast cells provides additional evidence of dissimilarity between mast cells and basophils, and an immunochemical means to distinguish between them.

The relationship of mast cells (MCs) to other blood leucocytes, and to basophils in particular, is unclear. The relative distribution and abundance of cell surface glycoproteins of normal and neoplastic blood cells has been established as providing a "fingerprint" allowing assignment to a particular hemopoietic cell lineage. We have examined the major labeled glycoproteins of mast cells, basophils, HL-60 cells (granulocytic), and U937 cells (monocytic), after cell surface tritiation by the periodate-borohydride technique. Mast cells have a characteristic glycoprotein profile, different from that of basophils and other leukocytes; a major feature is the lack of the gp105-115 molecular weight band common to all other white blood cells. The data suggest that the tissue mast cell is more distantly related to other hemopoietic cells than has been previously recognized.

The anaphylactic function of IgE has been intensively investigated. The Fc epsilon receptor on mast cells or basophils combines with the last two constant domains of the epsilon heavy chain. The Fc epsilon receptor is apparently a glycoprotein, monovalent and free in the plasma membrane. The interaction between the antigen (allergen) and the corresponding IgE antibody combined with the Fc epsilon receptor results in the aggregation of the receptors. Receptor dimerization suffices to trigger the cell. Compartments can be described in mast cells or basophils, the activity of which depends upon the number of formed receptor dimers on the corresponding membrane area. Beyond a threshold number of dimerized receptors, the cell compartment is triggered, which in the presence of Ca++ leads to the discharge of mast cell mediators, an increasing function of the dimer number. Excess receptor aggregation or the absence of aggregation (i.e. IgE-Ag2 complexes) deactivates the cell, which occurs more often in the absence of Ca++. Thus, IgE molecules play a passive role only in allowing the aggregation of the receptors which delivers the activating signal. But through the composition of IgE-antigen complexes bound to the receptors, IgE also modulates the cell function according two antagonistic reactions in permanent balance, i.e. activation or deactivation. IgE molecules are also involved in immediate type reactions in inducing the release of lysosomal enzymes from mononuclear phagocytes. But IgE antibody can also, when complexed with the antigen, trigger macrophage cytotoxicity for the corresponding target, which indicates a new function of IgE in the effector mechanisms of immunity of particular importance in immunity to schistosomes. A receptor for aggregated IgE has been characterized on the membrane of macrophages. The binding of IgE to its macrophage receptor triggers the cell, as shown by the resulting increase in cyclic GMP, calcium uptake and accelerated turn-over of lysosomal enzymes. A receptor for IgE has also been described on lymphoid cells, B cells, null cells and recently T cells, and the appearance of the receptor is modulated by IgE molecules themselves, suggesting a homeostatic role of IgE molecules. IgE appears thus to play various functions, the most dramatic being the triggering of anaphylactic reactions. But the role of IgE in activating mononuclear phagocytes or lymphoid cells might also prove to be of importance in immunity.

Mast cells were studied by light microscopy in mucosal imprints and in biopsies of nasal mucosa of 12 birch pollen allergic individuals before and during the pollen season, using techniques optimized for the demonstration of mucosal mast cells. We also measured the histamine content of nasal mucosa, whole blood and plasma, and counted the numbers of circulating blood basophils. Before the pollen season the nasal mucosa was found to contain many mast cells located in the mucosal connective tissue stroma, and very few cells with basophilic and metachromatic granules were found in mucosal imprints. During the pollen season there was a redistribution of mast cells into the epithelium, many such cells now being recovered in mucosal imprints. The total number of mucosal mast cells counted in tissue sections did not change significantly with the onset of the pollen season, suggesting a redistribution of mucosal mast cells by migration. Judged by morphologic appearance and naphthol-AS-D chloroacetate esterase activity, the intraepithelial mast cells found in tissue sections had rather the properties of tissue mast cells than of blood basophils, and only a few of the basophilic cells of the imprints had a morphology compatible with blood basophils. The histamine content of the mucosa, as well as histamine levels of whole blood and plasma, and circulating blood basophil numbers did not change significantly in relation to the pollen season. These findings suggest that an intraepithelial migration of mucosal mast cells is part of the allergic mucosal response.(ABSTRACT TRUNCATED AT 250 WORDS)

It could be shown that DAPI, a newer fluorochrome (4',6-diamidino-2-phenylindole), is able to stain various types of acid mucopolysaccharides, e.g. heparin and agar mucopolysaccharides. Due to their content of heparin, mast cells and basophil cells could be stained rapidly. Other cells e.g. mononuclear phagocytes and malignant epithelial cells, could be loaded with these acid mucopolysaccharides and subsequently stained by DAPI.