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Platelet aggregation and histamine release by immunological stimuli
E Masini1, M G Di Bello, S Raspanti
1Department of Preclinical and Clinical Pharmacology, Florence University, Italy.
Immunopharmacology
|July 1, 1994
Summary
Platelets release histamine and aggregate when exposed to anti-IgE, especially after IgE pretreatment. An H1-receptor blocker, loratadine, reduced these platelet responses.
Area of Science:
- Immunology
- Hematology
- Pharmacology
Background:
- Platelets contain and release histamine, a mediator involved in allergic reactions.
- Immunoglobulin E (IgE) plays a crucial role in allergic responses, but its direct effect on platelets is not fully understood.
Purpose of the Study:
- To investigate the role of IgE in human platelet aggregation and histamine release.
- To examine the effects of anti-IgE antibodies on IgE-sensitized platelets.
- To evaluate the efficacy of loratadine in modulating these IgE-mediated platelet responses.
Main Methods:
- Human platelets (normal and from atopic donors) were pretreated with IgE and stimulated with IgE, anti-IgE, or thrombin.
- Platelet aggregation was measured, and histamine release was quantified using fluorimetric analysis.
- Platelet morphology was assessed via electron microscopy; the effect of loratadine was also studied.
Main Results:
- Thrombin induced dose-dependent platelet aggregation and histamine release, effects amplified by IgE pretreatment.
- Anti-IgE induced significant aggregation and histamine release in IgE-pretreated or passively sensitized platelets, and in platelets from atopic donors.
- Loratadine (H1-receptor blocker) significantly reduced anti-IgE-induced platelet aggregation and histamine release.
Conclusions:
- IgE can sensitize human platelets, leading to aggregation and histamine release upon subsequent anti-IgE challenge.
- The anti-IgE-induced platelet response mimics thrombin-induced responses morphologically.
- H1-receptor blockade effectively inhibits IgE-mediated platelet activation, suggesting a role for histamine signaling in these events.