The response of basophil cytosolic free Ca2+ concentrations ([Ca2+](i)) to stimulation by eosinophil granule major basic protein (MBP) was assessed using digital video microscopy. MBP stimulated an elevation in basophil [Ca2+](i) that, in general, developed slowly and increased monotonically. In some experiments, however, the average rise in [Ca2+](i) was biphasic, with an initial transient increase followed by a larger and more sustained elevation. At the single cell level MBP stimulation caused frequent, asynchronous oscillations in [Ca2+](i) that ranged up to 300 nM in amplitude. Chelation of extracellular Ca2+ selectively blocked the second, sustained rise in [Ca2+](i) as well as MBP-induced histamine release. Within individual experiments, the increase in [Ca2+](i) paralleled the level of histamine release. These results demonstrate that, unlike the activation of neutrophils or eosinophils, basophil activation by MBP correlates with an elevation in [Ca2+](i). Further, the MBP induced [Ca2+](i) response exhibits several features in common with the IgE-mediated [Ca2+](i) response.
ASJC Scopus subject areas
- Immunology and Allergy