Which complement component is responsible for releasing histamine and other mediators from basophils?

The complement component responsible for releasing histamine and other mediators from basophils is C3a. It is classified as an anaphylatoxin, which means that it can provoke strong inflammatory responses. When C3a binds to its receptors on basophils and mast cells, it triggers degranulation, leading to the release of histamine and various other inflammatory mediators. This process is fundamental in amplifying the inflammatory response during immune reactions, such as those seen in allergic responses.

While C5 is involved in the complement cascade and can produce C5a, which also acts as a potent anaphylatoxin, it is the action of C3a that directly targets basophils for histamine release. C4a and C2 do not play a significant role in this specific mechanism of histamine release, as they do not possess the same effect on basophils or mast cell activation. Understanding the distinct roles of these complement components in the immune response is crucial for comprehending how they contribute to inflammation and allergy.