MAST-CELLS CULTURED FROM THE PERIPHERAL-BLOOD OF NORMAL DONORS AND PATIENTS WITH MASTOCYTOSIS ORIGINATE FROM A CD34-) CELL-POPULATION( FC(EPSILON)RI()

Mast cells may be cultured from human peripheral blood in the presence of recombinant human stem cell factor (rhSCF). The characteristics of the cells in peripheral blood that give rise to mast cells are unknow n. Because mast cell precursors in human marrow are CD34(+), human per ipheral blood mononuclear cells from patients with mastocytosis and no rmal controls were sorted on the basis of CD34 expression and the posi tive and negative cell populations were cultured in rhSCF, recombinant human interleukin-3 (rhIL-3), or both for 6 weeks. Cell cultures were examined every 2 weeks for total and mast cell number and cell differ ential using Wright Giemsa and acid toluidine blue stains and antibodi es to mast cell tryptase and chymase, cell-associated histamine, and e xpression of CD34, c-kit, Fc(epsilon)RI, and Fc(gamma)RII using flow c ytometric analysis. The ultrastructural anatomy of mast cells was exam ined by electron microscopy. Peripheral blood CD34(+) cells cultured i n rhSCF with or without rhIL-3 gave rise to cell cultures consisting o f greater than 80% mast cells by 6 weeks. CD34(+) cells cultured in rh IL-3 alone did not give rise to mast cells, whereas rhIL-3 plus rhSCF increased the final mast cell number eightfold when compared with cell s cultured in rhSCF alone. Mast cells increased concomitantly with a d ecrease in large undifferentiated mononuclear cells. CD34(-) cells did not give rise to mast cells. Histamine content per cell at 6 weeks wa s approximately 5 pg. Electron microscopy of 4-week cultures showed im mature mast cells containing predominantly tryptase-positive granules that were either homogeneous or contained lattice structures, partial scroll patterns, or central dense cores and mixtures of vesicles, fine granular material, and particles. The CD34(+) population at day 0 exp ressed Kit (65%) and Fc(gamma)RII (95%), but not Fc(epsilon)RI, by flu orescence-activated cell sorter analysis. At 6 weeks, CD34(+)-derived mast cells exhibited Fc(epsilon)RI in addition to Kit and Fc(gamma)RII , and were negative for CD34 antigen. Patients with mastocytosis showe d a higher number of mast cells per CD34(+) cell cultured compared wit h normal controls. Thus, the mast cell precursor in human peripheral b lood is CD34(+)/Fc(epsilon)RI(-) and gives rise to mast cells in the p resence of rhSCF with or without rhIL-3, and the number of mast cells arising per CD34(+) cell in culture is greater when the CD34(+) cells are obtained from patients with mastocytosis compared with normal subj ects. This is a US government work. There are no restrictions on its u se.