basophils

Basophils are granulocytes packed with granules that stain basic (purple with H&E).

The nucleus is bilobed, and the metachromatic granules contain sulfated glycosaminoglycans as well as vasoactive compounds – histamine and proteoglycans. Lysosomal arylsulfatase is found in granules of developing basophils in bone marrow.

Basophil granules are surrounded by a unit membrane and contain particles which are uniform in size across the same granule yet vary in size in different granules within the same cell. Some granules reveal a homogeneous texture and/or "myelin" figures. [s] Though basophils and mast cells share morphological features, the appearance of most basophil granules differs from the ultrastructure of human mast cell granules.

Activated basophils release proinflammatory histamine and proteoglycans from granules, and synthesize then secrete leukotrienes and cytokines (particularly IL-4). Histamine and IL-4, which is associated with production of IgE, are involved in allergic reactions.

Basophils are the least common granulocyte, representing about 0.5% to 1% of circulating leukocytes. A low basophil count combined with a low neutrophil count almost always portends leukemia.

Tables  Fc receptors  Immune Cytokines  Immunoglobulins .

tags [Immunology][leukocytes]

eosinophils

Eosinophils (acidophils) are granulocytes packed with granules that stain acidic (red with H&E). Eosinophils combat parasitic infection, and have diverse immune responsibilities.

Eosinophils play roles in:
● combatting viral infections (RNAses)
● allergic response
● fibrinolysis (following inflammation).
● pathogenesis of asthma
● combatting helminthic colonization, other parasites.

The acidophilic granules contain proteolytic enzymes that are toxic to parasite and elicit allergic symptoms in the host. The enzymes include histaminase, peroxidase, RNase, DNases, lipase, plasminogen, and Major Basic Protein. Eosinophils also secrete IL-5.

Eosinophils normally comprises about 2.3% of leukocytes, and elevations (eosinophilia) are associated with parasitic infestation, collagen vascular diseases (such as rheumatoid arthritis), malignancies such as Hodgkin's lymphoma, allergic skin conditions (such as exfoliative dermatitis), Addison's Disease, and hypersensitivity to drugs such as penicillin.

Tables  Fc receptors  Immune Cytokines  Immunoglobulins

tags [Immunology] [leukocyte]