IMMORTALIZATION AND CHARACTERIZATION OF HUMAN CELL-LINES WITH MAST-CELL AND MONOCYTIC PROPERTIES

We have previously derived a cell strain which had both mast cell and monocytic properties from the bone marrow of a child with diffuse cuta neous mastocytosis. This cell strain, termed HBM-M, consisted of two c ell populations both of which possessed certain ultrastructural, cytoc hemical and surface phenotypic features of degranulated mast cells. Th e cells also displayed cytochemical and surface phenotypic features of monocytes. These cells may represent a common bone marrow derived mas t cell/monocyte precursor. Studies of human mast cells have been hinde red by the fact that it is difficult to establish such cells in long-t erm culture. Thus, we sought to immortalize HBM-M cells by introducing Simian virus 40 large T-antigen. Following transfection by the stront ium phosphate technique, transformed cells were selected, expanded and passaged until the cells entered a non-proliferative phase termed cri sis. Certain clones passed through crisis 3 months later and by this m eans two immortal cell lines, HBM-MI-1 and HBM-MI-2, were obtained. Th e criterion for immortality was growth for greater than 100 population doublings. The immortal cell lines retained some, but not all, of the mast cell and monocytic properties of the original HBM-M cell strain. The immortalization of the cell strain HBM-M provides an opportunity to investigate the mast cell and monocytic properties of these cells, and the apparent relationship between mast cells and monocytes.