Abundance of Mast Cells

Mast cells are abundantly found in:

Correct Answer: Lung

Mast cells are most abundantly found in the lungs. This is because the lung is the organ most vulnerable to emboli (clots entering blood vessels), and mast cells secrete heparin (a natural anticoagulant) to protect against intravascular clotting in the pulmonary vasculature.

Key Facts About Mast Cells

• Mast cells are tissue-resident cells derived from bone marrow progenitors
• They are histologically similar to basophils — both produce heparin, histamine, serotonin, bradykinin & lysosomal enzymes in areas of inflammation
• Mast cells are found in connective tissue, especially near blood vessels, nerves, and epithelial surfaces
• They are important in allergic reactions and anaphylaxis (IgE-mediated degranulation)

Mast Cells vs. Basophils

• Basophils: Circulate in the blood; enhance allergic reactions
• Mast cells: Reside in tissues (especially lung, skin, gut); similar granules; protect tissues
• Key similarity: Both release heparin (anticoagulant) and histamine (allergen/vasodilator)
• Key difference: Eosinophils dampen allergic reactions (inactivate histamine), while basophils enhance them