THE MAST CELLS 



anaphylactic process generally, but that the mast cell is the common target 

 whenever a massive liberation of tissue histamine occurs.* 



Effect of antihistamines 



Antihistamines are thought to act either by blocking tissue receptors 

 against circulating histamine or by preventing the release of histamine (Dale). 

 Unfortunately, the actual mechanism is not yet known. Nevertheless, it is of 

 interest that premedication of rats with an antihistamine effectively protects 

 the mast cells against the disruptive action of histamine-liberators or ana- 

 phylatoxin. In this at least the results support the view, stated in the previous 

 paragraph, that the changes in the mast cells brought about by histamine- 

 liberators are significantly related to the phenomenon of histamine release. 



* It should perhaps be noted here, as Sir Henry Dale (1954) points out, that the anaphylactic 

 process in the rabbit follows a somewhat different pattern: the reaction occurs in the blood rather 

 than in the tissues. The rabbit is also exceptional in that the bulk of its histamine is located in the 

 blood platelets (Schayer and Kobayashi, 1956; Waalkes et a/, 1957). 



70 



