Role of mast cells in allergy had remained undetermined until the discovery of IgE in 1966. Then, IgE purified from many Liters of plasma, which had been donated from a patient with fatal myeloma, was distributed to researchers all over the world (http://buff.ly/12sD3cO).
Mast cells are present in nearly all vascularized tissues, but not the blood.
Mast cells. Image source: Wikipedia.
Mast cells are best known for their prominent in atopic disease but that is not all they do. Mast cells seem to have a more nuanced behavior of both villain and hero.
Although they are implicated in many inflammatory disorders, they also defend us from bacterial pathogens, prevent dangerous overreactions by the immune system, and even protect us from snake venom.
Mast cell modulation of the immune response. Ryan JJ, Fernando JF. Curr Allergy Asthma Rep. 2009 Sep;9(5):353-9.
Mast cells: makers AND breakers of allergic inflammation
Mast Cells and Basophils
Mnemonics: Mast Cells and Basophils
Mind Maps: Mast Cells and Basophils
Mast Cell Disorders (presentation on Google drive):