Final answer:
Eosinophils are granulocytes that make up 2-4% of the white blood cells and have a bilobed nucleus. They contain granules that stain with eosin and are involved in the immune response, particularly against parasitic worms and in allergic reactions. Abnormal eosinophil counts can indicate medical conditions such as allergies, infections, or stress.
Step-by-step explanation:
Eosinophils are a type of white blood cells, specifically a form of granulocytes. They typically represent 2-4% of the total leukocyte (white blood cell) count in the human body. These granulocytes are roughly 10-12 µm in diameter and are known for their distinctive granules that stain red to orange with an acidic stain called eosin. Eosinophils are visible under a microscope by their bilobed nucleus and granular inclusions in the cytoplasm.
Eosinophils play a vital role in the body's immune response, particularly in defending against parasitic infections and playing a part in allergic reactions. Their granules contain antihistamine molecules, which help to counteract the effects of histamines, and substances that are toxic to parasites, aiding in dealing with infestations. Eosinophils are also capable of engaging in phagocytosis, which is when they ingest foreign particles or organisms, especially when these targets are coated in antibodies, forming an antigen-antibody complex.
Abnormal levels of eosinophils can be indicative of various medical conditions. High counts of eosinophils may suggest the presence of allergies, parasitic infections, or certain autoimmune diseases, while low counts might be a sign of drug toxicity or stress. It's important to monitor the levels of eosinophils as part of a complete blood count (CBC) to help diagnose various health issues.