Granulocytes are a type of white blood cell, playing a part in the body’s immune system. These cells are essential for defending against different threats. They contribute to the body’s ability to respond to infections and other foreign substances.
What Granulocytes Are
Granulocytes are a type of white blood cell distinguished by small, visible granules within their cytoplasm. These granules contain enzymes and immune substances released to combat invaders. Produced in the bone marrow, granulocytes are part of the innate immune system, providing the body’s first line of defense. They have a multi-lobed nucleus, giving them the alternative name polymorphonuclear leukocytes. Their short lifespan, often lasting only a few days, requires continuous bone marrow production.
The Specific Types of Granulocytes
There are three primary types of granulocytes, each with distinct roles: neutrophils, eosinophils, and basophils. Neutrophils are the most abundant, making up 55% to 70% of all white blood cells. They are the immune system’s first responders, quickly migrating to sites of infection or injury.
Eosinophils make up 1% to 3% of white blood cells. These cells are involved in allergic reactions and combating parasitic infections. Their granules stain reddish-orange.
Basophils are the least common granulocyte, making up less than 1% of white blood cells. Despite their low numbers, basophils contribute to allergic responses by releasing histamine and other chemical mediators. Their granules stain dark blue or purple.
How Granulocytes Protect Your Body
Granulocytes defend the body by responding to foreign invaders and mediating inflammatory responses. Neutrophils, the most numerous type, primarily engage in phagocytosis, engulfing and digesting bacteria, fungi, and other microorganisms. This neutralizes pathogens, preventing infection spread. Neutrophils also release antimicrobial proteins and enzymes into the phagosome (the vesicle containing the engulfed pathogen) or surrounding environment.
Eosinophils and basophils utilize degranulation, releasing granule contents to combat threats or influence immune responses. Eosinophils release toxic substances effective against parasites and contribute to allergic reaction symptoms. Basophils release histamine, which increases blood flow to damaged tissues and prevents clotting, and other mediators contributing to allergic symptoms like itching and swelling.
Why Granulocyte Levels Matter
Maintaining appropriate granulocyte levels is important for effective immune function. Deviations from normal ranges indicate underlying health issues. An abnormally high count, known as granulocytosis, suggests ongoing infection, inflammation, or certain blood disorders. The body increases granulocyte production to combat these challenges.
Conversely, a low granulocyte count weakens the immune system, increasing susceptibility to infections. These imbalances highlight the cells’ importance in the body’s defense against pathogens and irritants. Monitoring granulocyte levels provides insights into immune status and overall health.