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Human bone marrow cells grown in liquid culture in the presence of conditioned medium from concanavalin A stimulated peripheral blood mononuclear cells, from mixed lymphocyte reactions, or from an osteogenic sarcoma tumor line gave rise to basophils which were maximal in number at 1-3 weeks. Basophils had a multilobed nucleus, contained large cytoplasmic granules of variable size which stained metachromatically with acid, but not neutral toluidine blue, were negative for chloroacetate esterase, and did not contain human mast cell tryptase. In long-term cultures, mast cells were detected after 5-6 weeks. Mast cells had cytoplasmic granules that stained with acid and neutral toluidine blue, were positive for chloroacetate esterase, and contained human mast cell tryptase. It, therefore, appears that in liquid cultures even in the absence of feeder layers, human bone marrow cell cultures can give rise initially to basophils, and then to mast cells.

It has long been recognized that mast cells occur throughout connective tissues. Histologic studies have revealed that such cells release their granules into the surrounding environment upon exposure to both immunologic and nonimmunologic stimuli. By microscopy these extracellular granules appeared to be phagocytosed by fibroblasts and by blood-borne phagocytic cells as they entered the site of mast cell degranulation. Such in vivo observations led to the suggestion that mast cells both altered connective tissue components and influenced fibroblast function through these discharged granules. Recent in vitro studies using cultured fibroblasts and isolated mast cells and mast cell granules have confirmed both these hypotheses. In addition, such studies have also documented that fibroblasts degrade ingested mast cell granules. Such studies document that a number of critical interactions may occur between mast cells and connective tissue components.

In order to determine whether mast cells or basophils could be derived from nonhuman primate bone marrow, cells from bone marrow aspirates were cultured in the presence of concanavalin A-stimulated nonhuman primate spleen cell supernatants (CAS). Culture conditions were identical to those used for culturing mucosal-like mast cells from mouse bone marrow. In this situation, basophil-like cells (BLC) could be identified in liquid cultures and averaged 14-19 microM in size, were round or oval in appearance, had lobulated nuclei, and contained less than 100 metachromatically staining granules per cell. By electron microscopy, granules had dense oval or semilunar cores with surrounding fibrous whorls. BLC were peroxidase positive, chloroacetate esterase negative, stained positively with acid toluidine blue, and contained 0.1-0.3 pg histamine per cell. BLC expressed IgE receptors and were Leu 5b and Leu 16 negative. IgE-sensitized BLC released histamine after stimulation with antihuman IgE or the calcium ionophore A23187. [35S]-labeled proteoglycans were degraded with chondroitinase ABC but not with heparinase, indicating the absence of heparin in BLC. Thus, culture conditions that include the use of CAS and lead to the growth of mast cells from rodent bone marrow result in the growth of BLC from nonhuman primate bone marrow. These observations suggest that fundamental differences exist in the type of histamine containing cells that arise from rodent and primate bone marrow when such bone marrow cells are cultured under identical conditions.