| Abstract: | Selective growth of human basophilic granulocytes was obtained in suspension cultures of mononuclear cells from umbilical cord blood. Approximately 50 to 80% of nonadherent cells recovered from 2- to 3-wk-old cultures contained metachromatic granules, and these cells were identified as human basophilic granulocytes by electron microscopy. Histamine content of cultured human basophils was comparable to that in peripheral blood basophils. Cultured basophils bear 2.7 to 3.7 X 10(5) IgE receptors per cell that bind both human IgE and rodent IgE with comparable affinity. Average equilibrium constants of the receptors for human IgE and mouse IgE were 2.56 +/- 0.88 X 10(9) M-1 and 1.85 +/- 0.86 X 10(9) M-1, respectively. The cell-surface component of the IgE receptors on cultured basophils has a m.w. of 64,000. Cultured basophils could be passively sensitized with human IgE and mouse IgE monoclonal antibody, and sensitized basophils released characteristic cytoplasmic granules and both histamine and arachidonate upon challenge with either anti-human IgE or antigen. Incubation of cultured basophils with ionophore A23187 or F-Met-Leu-Phe resulted in histamine release. However, compound 48/80 failed to induce histamine release from the cells. |
