What Are White Blood Cells?
White blood cells, scientifically known as leukocytes, are crucial components of the body's immune system, acting as its primary defense against infection and disease. Unlike red blood cells, which transport oxygen, leukocytes are specialized cells that identify and destroy foreign invaders like bacteria, viruses, fungi, and parasites. They originate in the bone marrow and circulate throughout the bloodstream and lymphatic system.
Types and Functions of Leukocytes
There are several distinct types of white blood cells, each with unique functions. These broadly fall into two categories: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes and monocytes). Neutrophils are the most abundant and are quick responders to bacterial infections, engulfing pathogens. Lymphocytes (T-cells and B-cells) are critical for specific immunity, recognizing and remembering particular invaders, while monocytes mature into macrophages, large cells that clean up cellular debris and pathogens.
How White Blood Cells Fight Infection
When a pathogen enters the body, white blood cells are activated and travel to the site of infection. For instance, in a bacterial infection, neutrophils rapidly migrate and perform phagocytosis—ingesting and destroying the bacteria. During a viral attack, T-cells identify and destroy infected cells, while B-cells produce specific antibodies to neutralize the virus. This coordinated cellular response ensures effective removal of threats and prevents illness.
Importance in Health and Disease Diagnosis
White blood cells are indispensable for maintaining health, as they continuously guard against potential threats. Their levels are a key indicator in routine blood tests, offering insights into a person's health status. Elevated white blood cell counts can signal an ongoing infection or inflammatory condition, while abnormally low counts may indicate a weakened immune system or certain bone marrow disorders, making them vital for medical diagnosis.