Origin of human mast cells studied by dual immunofluorescence.

Previous reports have suggested that mast cells derive either directly from basophils or mononuclear phagocytes, or from a common myeloid precursor. We have used monoclonal antibodies to investigate expression by normal human tissue mast cells of antigens characteristic of other haemopoietic lineages. We find that mast cells express panhaemopoietic markers, but not antigens typical of either myeloid or lymphoid cells. We propose, therefore, that mast cells form a distinct lineage, only distantly-related to other haemopoietic cells.

Cell membrane glycoproteins of human mast cells: a biochemical comparison with basophils.

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.

Giant cell formation in rabbit long-term bone marrow cultures: immunological and functional studies.

A method for the long-term culture of rabbit newborn bone marrow has been developed. It is characterized by the rapid appearance of an adherent, adipocyte-containing stromal layer, proliferation of mature myeloid cells, and the formation of numerous, large multinucleate giant cells. By the combined use of morphological, immunological, and functional criteria these giant cells have been characterized as macrophage polykaryons and not osteoclastic giant cells. We conclude that long-term bone marrow culture in the rabbit favors the proliferation, maturation, and fusion of macrophage, but not osteoclast, precursors--new experimental models will have to be developed to enable the developmental biology of osteoclasts to be studied in the rabbit.

In-vitro culture of basophils from human bone marrow.

An in-vitro culture system is described in which metachromatically granulated leucocytes differentiate from human bone marrow under stimulation by conditioned medium from the 5637 cell line. By morphological, cytochemical and immunophenotypic criteria these were shown to be basophils, rather than mast cells. This system may prove useful in studies of basophil differentiation, and in characterisation of growth factors active upon basophil precursors. The study also identified the 5637 bladder carcinoma cell line as a constitutive producer of basophil growth factor(s); this may represent a convenient source for the isolation and purification of such factors.

On the origin of the osteoclast: the cell surface phenotype of rodent osteoclasts.

The origin and development of the osteoclast is not well defined; although it is derived from a bone marrow stem cell, it is not proven whether the osteoclast progenitor comes from the multipotential hemopoietic stem cell or comprises an entirely separate cell lineage. We have studied the cell lineage relationship of osteoclasts isolated from newborn rodent bone to other bone marrow cell types, in particular the monocyte-macrophage cell line, by the use of cell surface phenotyping. In studies in mouse and rat we failed to detect the expression of markers characteristic of mononuclear phagocytes or other bone marrow cell types, including the hemopoietic tissue restricted common leucocyte antigen (T200). Our findings cast further doubt on the view that osteoclasts arise by fusion of mononuclear phagocytes in a similar fashion to the formation of multinucleate inflammatory giant cells.

Cell surface characterization of the human osteoclast: phenotypic relationship to other bone marrow-derived cell types.

Among the differentiated progeny of stem cells transplantable by bone marrow are osteoclasts, the multinucleate cells which are the major agents of bone resorption. Although the osteoclast is well characterized from a structural and functional standpoint, its development and origin are still far from clear. We have used monoclonal antibodies to investigate the interrelationship between osteoclasts and other haemopoietic cells in man. We have analysed the distribution of 19 granulocyte-monocyte antigens in eight reactivity clusters on the non-neoplastic osteoclasts present within nine osteoclastomas (syn. giant cell tumours of bone) and a single example of aneurysmal bone cyst. We found that osteoclasts are antigenically effete, failing to express granulocyte-monocyte, common leucocyte or other haemopoietic determinants; the only monocyte antigens detected on osteoclasts are My-7 and two closely related specificities, MCS.2 and DüHL60.4, which are also expressed by tissues outside the haemopoietic system. Our findings, taken together with recent transplantation studies, cast further doubt on the view that osteoclasts are specialized bone-resorbing macrophage-derived giant cells, and support a hypothesis that they are the end product of fusion of a hitherto unidentified circulating mononuclear cell type, the preosteoclast, which constitutes a cell lineage separate from those originating from the conventional multipotential haemopoietic stem cell, although still of bone marrow origin.

Human mast cells detected by monoclonal antibodies.

We report the establishment of seven mouse-mouse hybridoma cell lines secreting monoclonal antibodies with specificity for granule components of all human mast cells. Reactivity is directed against a molecule which is also found intracytoplasmically in human mature small intestinal enterocytes, liver parenchymal cells, and kidney proximal tubule epithelial cells. No reactivity of these antibodies was found with any other human or animal cell type examined. In particular, the antibodies did not react with basophils or other haemopoietic cell types. This study shows the potential of specific monoclonal antibodies as a tool for identifying and enumerating infiltrating mast cells in tissues. Such antibodies should be of value in investigations into the role of the mast cell in immunological reactions and hypersensitivity diseases.

Expression of myeloid-specific antigens on two human erythroleukaemia cell lines, HEL and K562.

The cell-surface phenotype of the human erythroleukaemia cell line, HEL, was investigated using a panel of lineage-specific monoclonal antibodies by indirect immunofluorescence. Antigens specific for the erythroid, granulocytic and monocytic lineages were detected, but no lymphoid- or platelet-specific antigens were found. The data obtained for HEL were compared to findings for the K562 human erythroleukaemia cell line and considerable similarities were demonstrated between the phenotypes of the two. In particular it was noted that the majority of granulocyte/monocyte markers present on HEL were also present on K562. The occurrence on HEL of markers of several haemopoietic lineages would suggest an origin from the non-lymphopoietic multipotential stem-cell or CFU-GEMM.