8499
Mast cells are derived from hematopoietic progenitors that are known to migrate to and reside within connective and mucosal tissues , where they differentiate and respond to various stimuli by releasing pro - inflammatory mediators , including histamine , growth factors , and proteases .
 histamine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 histamine