IgE and adenosine 5' triphosphate receptors on immature murine mast cells are functionally linked to signal transduction mechanisms.

Calcium mobilization in response to IgE-receptor cross-linking by antigen was assessed in immature murine mast cells cultured from bone marrow to determine whether the early expression of IgE receptors on such cells may be of functional significance. IgE receptors were expressed by approximately 30% of cells after 1 week in culture and by an increased proportion at 2 and 3 weeks. The ability of a non-IgE-dependent stimulus, adenosine 5' triphosphate (ATP), to increase intracellular calcium in these cells was also tested. Calcium mobilization in large numbers of individual cells was monitored with use of a fluorimetric reagent and flow cytometry. Both antigen and ATP had significant effects on intracellular calcium in cells cultured for as little as 1 week with interleukin-3, when few cells exhibited morphologic or functional characteristics of mast cells. Longer times in culture were associated with an increase in the proportion of cells responding to these stimuli with calcium mobilization, but not with a change in the magnitude of the response. We conclude that the early expression of IgE receptors during mast cell development may be functionally significant, since these receptors appear to be linked to cellular signal transduction mechanisms. The data additionally imply a possible role for ATP in mast cell development.