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Clinical & Experimental Allergy

Platelet-activating factor: a possible mediator of the dual response to allergen?



Certain allergic asthmatic patients exhibit a dual response in the lung following bronchial challenge with the appropriate allergen, Often this is paralleled by a cutaneous dual response when the antigen is injected intradermally. The mechanisms underlying such phenomena are not established, but some evidence suggests that the late response is a consequence of the early response. Since platelet activation has been observed following antigen challenge in asthmatic subjects, we have studied the ability of platelet activating factor (PAF-acether. AGEPC) to induce cutaneous inflammatory responses in man. In a time course study over 24 hr, PAF-acether produced a biphasic response: an immediate weal and flare reaction, which resolved within 1-2 hr and was followed some 3-6 hr later by a delayed reaction in which erythema associated with hyperaigesia was evident. These observations suggest that PAF-acether should be considered in the context of allergic asthma as a possible mediator of the dual response to allergen.

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