Mast cells (which are Leukocytes ) contain metachromatic granules which store a variety of inflammatory mediators. These include:

• Histamine and serotonin .
• Proteolytic enzymes that can destroy tissue or cleave complement components.
• Heparin or chondroitin sulfate, which are anticoagulants.
• Chemotactic factors, such as eosinophil chemotactic factor of anaphylaxis (an important regulator of eosinophil function) and neutrophil chemotactic factor.