A dоg is brоught tо the clinic аfter being stung by а bee for the second time. Within minutes the dog collаpses, develops difficulty breathing, and has swollen lips and face. The owner mentions the first sting last summer caused only mild local swelling. In a well-organized essay, explain why the first sting was necessary for this reaction to occur, what happens at the molecular level when the dog is stung a second time, and which mediators are responsible for the clinical signs observed. In your answer, also explain why epinephrine is the treatment of choice and how it works at the receptor level to reverse the reaction.