COMPARATIVE ULTRASTRUCTURAL MORPHOLOGY OF HUMAN BASOPHILS STIMULATED TO RELEASE HISTAMINE BY ANTI-LGE, RECOMBINANT IGE-DEPENDENT HISTAMINE-RELEASING FACTOR, OR MONOCYTE CHEMOTACTIC PROTEIN-1

An ultrastructural analysis of human basophils stimulated with anti-Ig E, recombinant histamine-releasing factor (rHRF), or monocyte chemotac tic protein-1 (MCP-1) (compared with unstimulated cells) was performed . Partially purified peripheral blood basophils were prepared for elec tron microscopy at time points known to precede histamine release and at half-maximum histamine release times for each secretagogue. Activat ion morphologies associated with stimulation included granule-vesicle attachments, piecemeal degranulation, anaphylactic degranulation, and uropod formation. These features were qualitatively similar in the sti mulated samples. Quantitative differences were evident, however, when stimulated samples were compared with controls or at different time po ints after stimulation with a single agent or when individual secretag ogues were compared. All stimulated samples differed quantitatively fr om the control samples. Rank orders for morphologic activation events revealed that the most effective trigger for anaphylactic degranulatio n was anti-IgE>MCP-1>rHRF, whereas the most effective trigger for urop od formation was rHRF>anti-IgE>MCP-1. Rank orders for piecemeal degran ulation and granule-vesicle attachments were the same: MCP-1>anti-IgE> rHRF. Important relationships among these anatomic events reveal that the development of motile configurations is not associated with the de velopment of secretion morphologies and that piecemeal degranulation p recedes and is inversely related to anaphylactic degranulation in stim ulated samples.