Histamine and heparin, and constitute less than 1% of all white blood cells.

Basophils

Explanation:

Basophils are the granular leukocytes that make 0-1% of the total white blood cells. Basophils are 10–12 μm in diameter and are the spherical cells with lobed nuclei. When Wright stained, basophils appear to have large, irregularly shaped, deep-blue granules in their cytoplasm. These granules take up the basic stain and hence these cells are called basophils.

Basophils release histamine and heparin. Histamine is associated with allergic reactions. Histamine also dilates blood vessels and triggers contraction of smooth muscle. Heparin inhibits clotting and promotes blood flow. Together, histamine and heparin promote blood flow to injured tissues.

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