Characterization of human mast cells in long-term culture.

Recent studies in rodents have demonstrated that mast cells derived from lymphoid tissues can be grown in longterm culture, provided that supportive growth factors or stromal fibroblasts are added; such findings have not been reported in man. Furthermore, although a hemopoietic origin for mast cells is supported by transplantation studies in mice, the exact origin of the human mast cell or its relationship to the circulating basophil and other hemopoietic cell lineages is unknown. We have investigated the requirements for in vitro growth of human mast cells derived from the infiltrated bone marrow of a patient with systemic mastocytosis, and have characterized both the mast cells proliferating in these cultures and those obtained from splenic infiltrates. Our data approached two questions: (1) Is there any evidence for the origin of mast cells from a bone-marrow-derived stem cell, and, if so, (2) what lineage relationship is there between mast cells and granulopoietic cells, including basophils? First, we have shown the expression of hemopoietic tissue-specific antigens by mast cells, strongly supporting a bone marrow origin for the mast cell in man (at least for those mast cells analyzed here). Second, the complete lack of granulocyte-monocyte markers contrasts with the phenotype of the basophil and suggests that mast cells diverge considerably from other granulopoietic cells during the acquisition of their differentiated specialized functions.