Final answer:
Eosinophils are granulocytes with a bilobed nucleus that stain red to orange with eosin and are involved in the body's response to allergic reactions and parasitic infections. They release antihistamines and toxic substances to combat these threats and can participate in phagocytosis when activated by antibodies. Abnormal levels of eosinophils can indicate various health issues like allergies, parasitic infections, and autoimmune diseases.
Step-by-step explanation:
Eosinophils are a type of white blood cell, specifically a type of granulocyte, that play a crucial role in the body's immune response. These cells are characterized by their granular cytoplasm and a bilobed nucleus. Their granules stain well with an acidic dye called eosin, giving them a distinct red to orange coloration when viewed under a microscope. Eosinophils are typically involved in the body's response to allergic reactions and parasitic infections. They contain granules with antihistamine molecules that can counteract the effect of histamines released by basophils and mast cells. These granules also contain toxic substances to parasites, making eosinophils effective against parasitic worms. Additionally, they participate in immune functions such as phagocytosis, especially when antibodies tag a target, forming an antigen-antibody complex. Elevated levels of eosinophils are often found in patients with allergies, parasitic infections, and some autoimmune diseases, while reduced levels can be an indication of drug toxicity or stress.