Types of White Blood Cells: There are several types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type has specific functions in combating different pathogens. Lifespan: White blood cells have a relatively short lifespan compared to other cells in the body. Most white blood cells live for only a few days to a couple of weeks. Production: WBCs are produced in the bone marrow through a process called hematopoiesis. Stem cells in the bone marrow differentiate into different types of white blood cells based on the body's needs. Function: White blood cells primarily function to defend the body against infections. They recognize and destroy foreign invaders, such as bacteria, viruses, and fungi, through various mechanisms like engulfing them, producing antibodies, and releasing chemicals to kill pathogens. Movement: White blood cells can move actively throughout the body by squeezing through the walls of blood vessels, a process called diapedesis. This allows them to reach the site of infection or inflammation. Phagocytosis: Some white blood cells, particularly neutrophils and monocytes, are phagocytes. They engulf and digest bacteria, cellular debris, and other foreign substances through a process called phagocytosis. Immune Response: Lymphocytes, a type of white blood cell, are the key players in the immune response. They are responsible for recognizing specific antigens and coordinating the body's immune response, including the production of antibodies. Leukocytosis and Leukopenia: Abnormal levels of white blood cells can indicate underlying health conditions. Leukocytosis is an increase in WBC count, often seen in response to infections, while leukopenia is a decrease in WBC count, which can be caused by certain medications, diseases, or bone marrow disorders. Allergies and Eosinophils: Eosinophils are white blood cells involved in allergic reactions and parasitic infections. They release substances that help regulate the immune response during allergic reactions. Diagnostic Importance: Measuring the number and types of white blood cells in a blood sample, known as a complete blood count (CBC), is a common diagnostic tool to assess a person's overall health and detect underlying conditions.