PATHOLOGY

Detailed explanation-1: -The kinin system, which is activated by coagulation factor XII, produces substances that increase vascular permeability. The most important of the kinins is bradykinin, which is responsible for much of the pain and itching experienced with inflammation.

Detailed explanation-2: -Histamine is a major preformed mediator released by mast cells and it strongly increases vascular permeability.

Detailed explanation-3: -Mast cells release mediators that increase both leukocyte adhesion to the venular endothelium and vascular permeability during reperfusion (47).

Detailed explanation-4: -Mast cells release histamine as well as other vasoactive molecules, which cause urticaria (hives). If the antigen activates mast cells in deeper tissue, this can lead to angioedema.