The basophils in the circulating blood are similar to the large tissue mast cells located immediately outside many of the capillaries in the body. Both mast cells and basophils liberate heparin into the blood, a substance that can prevent blood coagulation.
The mast cells and basophils also release histamine, as well as smaller quantities of bradykinin and serotonin. Indeed, it is mainly the mast cells ininflamed tissues that release these substances during inflammation.
The mast cells and basophils play an exceedingly important role in some types of allergic reactions because the type of antibody that causes allergic reac-tions, the immunoglobulin E (IgE) type, has a special propensity to become attached to mast cells and basophils. Then, when the specific antigen for the specific IgE antibody subsequently reacts with the antibody, the resulting attachment of antigen to antibody causes the mast cell or basophil to rupture and release exceedingly large quantities of histamine, bradykinin, serotonin, heparin, slow-reacting substance of anaphylaxis, and a number of lysosomal enzymes. These cause local vascular and tissue reac-tions that cause many, if not most, of the allergic man-ifestations.