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What Are the Functions of Leukocytes?

Leukocytes, or white blood cells (WBCs), are essential immune system components that defend the body against foreign materials and infectious diseases. There exist five types of leukocytes in the body, all derived from the hematopoietic stem cell of the bone marrow. Leukocytes are present in the lymphatic system and the blood, traveling to infected tissues and/or organs to attack the cause of the infection. White blood cells contribute to approximately 1 percent of the total volume of human blood in an adult.

  1. Defense Against Bacterial Infections

    • Neutrophils are a type of leukocytes that specialize in defending the body against bacterial infections. They charge in large numbers upon the disease-causing bacteria, activating and attacking the contaminant to neutralize the effect of the infection. They are most active in addressing phagocytosing bacteria. Diseases neutrophils protect against include tuberculosis, leprosy, cholera, syphilis, diptheria, typhoid fever and tetanus.

    Defense Against Parasitic Infections

    • Eosinophils are specialized white blood cells that address and neutralize parasitic infections. They also provide protection to the body in case of allergic reactions (hay fever, asthma and hives). Parasitic infections eosinophils provide defense against include babesiosis, giardia, malaria, sleeping sickness, chagas disease and worms (roundworm, tapeworm, hookworm, guinea worm, liverfluke and river blindness).

    Defense Against Allergic Reactions

    • Basophils, or basophil granulocytes, make up between 0.01 to 0.03 percent of white blood cells. They appear in inflammatory reactions, especially those that are caused by allergies. Basophils prevent the blood from clotting and release histamine to effectively manage the flow of blood to tissues and organs.

    Attacking Tumors and Virus-Infected Cells

    • Natural killer, or NK, cells are a type of lymphocyte (a category of WBC that functions in defending the body against tumors and virally infected cells. The other two types of lymphocytes include B cells and T cells) that defend the body against tumors (malignant, pre-malignant and benign). NK cells release cell-killing substances in granule form, which destroy all abnormal cells.

    Replenish Immune System Cells

    • Monocytes are a type of WBC that function to replenish key immune system components, such as dendritic cells (cells that process and supply antigen material to other immune system cells) and macrophages (WBCs that surround and digest all cellular debris and tissue waste). Monocytes move to the infected site and divide into macrophages and/or dendritic cells to initiate immune system defense. Monocytes ingest all foreign matter in the body and protect vital organs and tissues from invasive pathogens.

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