“Polys” is a common abbreviation seen on a complete blood count (CBC) with differential. The term is short for Polymorphonuclear Leukocytes, but clinically, it refers primarily to Neutrophils, the most plentiful type of white blood cell (WBC) in the human body. These cells are a subset of WBCs, which function collectively as the body’s immune system defense force. Analyzing the count and characteristics of Polys offers clinicians insight into whether an infection, inflammation, or other bodily stressor is present.
Polys Explained: Function in the Immune System
Polymorphonuclear leukocytes are known as professional phagocytes, equipped to seek out, ingest, and destroy invading microorganisms. They serve as the rapid-response team of the innate immune system, providing a non-specific defense. When a bacterial infection or tissue injury occurs, chemical signals called chemokines are released. These signals prompt Polys to quickly leave the bloodstream and migrate to the site of inflammation.
Once at the site of invasion, Polys use phagocytosis to engulf foreign particles, such as bacteria and fungi. The cell surrounds the pathogen, drawing it into a membrane-bound sac called a phagosome. Internal granules within the Poly then fuse with this sac, releasing powerful enzymes and reactive oxygen species that digest and kill the captured microbe.
Polys are continuously produced in the bone marrow, derived from hematopoietic stem cells. The body produces an enormous number of these cells daily, estimated at over 100 billion in a healthy adult. This high production rate is necessary because Polys have a relatively short lifespan. They often circulate for less than 24 hours before they are consumed or naturally cleared from the body.
Interpreting Polys Counts: What Do the Numbers Mean?
The most clinically meaningful measurement of Polys is the Absolute Neutrophil Count (ANC), which represents the actual number of circulating neutrophils per microliter of blood. The ANC is calculated by taking the total white blood cell count and multiplying it by the percentage of neutrophils and their immediate precursors, known as bands. This count provides a more accurate picture of the body’s infection-fighting capacity.
For a healthy adult, the typical ANC reference range is between 1,500 and 8,000 cells per microliter of blood, though specific laboratory ranges may vary. When the ANC is elevated above this range, the condition is termed Neutrophilia. Neutrophilia indicates that the body is actively mobilizing Polys to combat a threat or is reacting to physiological stress.
Conversely, a low ANC is referred to as Neutropenia, typically defined as a count below 1,500 cells per microliter. A low count signals a reduced capacity to fight infections, making the individual vulnerable to illness. The severity of Neutropenia is often categorized based on the count. Levels below 500 cells per microliter indicate a high risk of severe infection.
Common Causes of Abnormal Polys Levels
Neutrophilia, or an elevated Polys count, is most frequently caused by the body’s reaction to bacterial infections. Acute inflammation prompts the bone marrow to rapidly release neutrophils into the bloodstream. This surge is a defensive maneuver against invading organisms.
Other common causes of a high Polys count include physical or emotional stress, which triggers the release of hormones that mobilize neutrophils. Severe inflammation from conditions like rheumatoid arthritis, gout, or tissue damage (e.g., burns or trauma) can also lead to Neutrophilia. Certain medications, particularly corticosteroids, are known for causing an increase in circulating neutrophils.
Neutropenia, or a reduced Polys count, can arise from issues with production, destruction, or distribution. A common cause is treatment with chemotherapy or radiation, which suppresses the bone marrow’s ability to produce new blood cells, including neutrophils. Viral infections (e.g., influenza, measles, or HIV) can temporarily or chronically suppress neutrophil levels.
Autoimmune disorders, like lupus, can cause the immune system to mistakenly attack and destroy neutrophils. Certain medications, including antibiotics and anticonvulsants, can also trigger a reduction in circulating Polys. Nutritional deficiencies, such as a lack of vitamin B12 or folate, can impair the bone marrow’s ability to manufacture these cells.