|OCCUPATION||Chemical Release Manager|
|ANIME DEBUT||Episode 4|
|MANGA DEBUT||Chapter 2|
Mast Cell (マスト細胞 Masuto Saibō?) is a minor character in Cells at Work!.
She is a white blood cell, specifically a Mast Cell (mastocyte or labrocyte). As a part of the immune system, she releases chemicals such as histamines and leukotrienes as a stimulus to excess production of IgE (Immunoglobulin E, an antibody produced by B Cells).
She is a serene-looking cell with brown eyes and black hair that passes her shoulders, She wears a yellow t-shirt under a white lab coat with a long olive coloured that goes up to her knees with black/brown tights/pantyhose with a grey line pattern and white shoes.
Despite her appearance, she can be very fierce if she is unhappy, especially when her work is unappreciated. She is sometimes insecure about herself, as she is afraid to cause trouble for everyone when she overdoes her job. She gets very angry when people call her "Fat Cell", showcasing her insecurities, as seen in Episode 5 when B Cell blames her for all the destruction and calls her "Fat Cell". She, in return, yells that the B in his name must stand for Bonehead and after some back and forth arguing, they fight each other.