White blood cells (WBCs), also called leukocytes, are an important part of the immune system. They help the body identify and respond to infections, foreign substances, and other threats. Produced primarily in the bone marrow, different types of white blood cells perform different roles in protecting overall health.
The main types include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Neutrophils help fight many bacterial and fungal infections, while lymphocytes play important roles in immune responses. Monocytes help remove damaged cells and certain harmful organisms, and eosinophils and basophils are involved in specific immune and inflammatory responses.
A white blood cell count is commonly included in a complete blood count (CBC). Abnormally high or low WBC levels can occur for many reasons, including infections, medications, immune conditions, nutritional problems, or certain blood and bone marrow disorders.
If a blood test shows an unusual white blood cell count, the result needs to be interpreted alongside symptoms, medical history, and other laboratory findings. A hematologist can evaluate persistent or unexplained abnormalities and recommend further testing when appropriate.
Understanding white blood cells can help patients better understand their blood test results and the role of the immune system in maintaining health.