Mast cell

A mast cell is like a white blood cell (leukocyte) which lives and acts in tissues. It is made in bone marrow, and matures in tissues, where it defends against parasites.
Mast cells have many granules rich in histamine and heparin. Mast cells play an important protective role in wound healing and defence against pathogens. They are a part cause of allergy and anaphylaxis, 
The mast cell is very similar in both appearance and function to the basophil, a type of white blood cell. However, they are not the same. 
Mast cells were first described by Paul Ehrlich in his 1878 doctoral thesis. He noted the large granules visible once they were stained. They are now considered to be part of the immune system.