White blood cell
From Simple English Wikipedia, the free encyclopedia
White blood cells, or leukocytes, defend the body against pathogens. They also remove toxins, wastes and damaged cells from the blood. The different types of white blood cells are: lymphocytes, Monocytes, Neutrophils, Eosinophils and Basophils.
Lymphocytes are round cells slightly larger than a red blood cell. They have a round nucleus and very little cytoplasm. Part of the lymphatic system, these target specific pathogens or toxins. There are three known types of lymphocytes: T-cells, B-cells and NK or natural killer cells.
Monocytes are large cells with a kidney bean shaped nucleus and lots of cytoplasm. They may appear irregular in form as they enter tissues to engulf pathogens or cellular debris.
The next three types of white blood cells are referred to as granulocytes since they all contain grainy particles that assist in attacking pathogens.
Neutrophils are large round cells with a lobed nucleus, often thought to resemble a string of beads. the granules are neutral to stains so the cytoplasm appears pale in contrast to the nucleus. These white blood cells are phagocytitic, engulfing pathogens and debris. The granules contain lysosomal enzymes and bacteria-killing compounds.
Basophils are also large round cells. The lobed nucleus is obscured by granules which stain dark blue in response to a basic stain. Basophils release histamines and other chemicals that promote inflammation.
Eosinophils are round cells with a lobed nucleus and granules that turn red in response to acid stains. These are also phagocytes engulfing materials or cells labeled with foreign antibodies. Eosinophils also perform exocytosis (release cytotoxic enzymes)of their granules to attack worms and parasites that are too large to engulf. Eosinophils are sensitive to allergens and release enzymes that reduce inflammation.
A special test called a Differential count estimates the levels of each different type of white blood cell. These are used as a diagnostic indicator regarding the type of infections the body is fighting. Normal levels vary but the following are average percentages in a differential count: neutrophils: 50-70% lymphocytes: 20-30% Monocytes: 2-8% Eosinophils: 2-4% Basophils: >1%
