Platelet Activation in Antigen-Induced Bronchoconstriction

To the Editor: The interesting article on platelet activation in patients with asthma by Knauer and his colleagues¹ raised some questions that may be answerable by more recent information on platelet physiology. The authors suggested that the increased levels of the platelet-specific protein platelet factor 4 (PF4) after antigen challenge in their asthmatic subjects was related to the release of a basophil or mast-cell chemical mediator that activates platelets. However, it has recently been demonstrated that tissue mast cells contain PF4, which could have been either produced by the mast cells or exogenously acquired and bound to the heparin in.