How does the Human Immune System work?

White blood cells

White blood cells also called leukocytes (LOO-Kuh-sites), perform an essential role in the immune system. Some kinds of white blood cells, called phagocytes (FAH-guh-sites), eat up attacking organisms. Others, called lymphocytes (LIM-Fuh-sites), support the body memorize the enemies and kill them.

One kind of phagocyte is the neutrophil (NOO-truh-fil), which attacks bacteria. When someone might have a bacterial disease, physicians can request a blood test to detect if the body has produced lots of neutrophils. Other kinds of phagocytes do their works to ensure that the body reacts to enemies.

The two varieties of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes begin out in the bone marrow and either stay there and develop into B cells or move to the thymus gland to develop into T cells. B lymphocytes are like the body's army intelligence system - they discover their victims and send guards to lock onto them. T cells are like the volunteers - they kill the enemies that the intelligence system detects.

Antibodies

Antibodies aid the body to battle microbes or the toxins (poisons) they create. They do this by identifying essences called antigens on the outside of the microbe, or in the elements they produce, which identify the microbe or toxin as being different. The antibodies then identify these antigens for killing.

Spleen

The spleen is a blood-filtering gland that eliminates microbes and kills old or spoiled red blood cells.

Bone marrow

Bone marrow is the springy tissue located inside your bones. It originates the red blood cells our bodies require to transport oxygen, the white blood cells we employ to uphold infection, and the platelets we require to ease our blood clotting.

Thymus

The thymus filters and manages your blood content. It provides the white blood cells called T-lymphocytes.

Spleen

The spleen is a blood-filtering gland that eliminates microbes and kills old or spoiled red blood cells.

Macrophages

Macrophages are a kind of white blood cells and a part of our immune defense mechanism. They are produced in our bone marrow. They recognize, surround or cover the foreign body, and then defeat the foreign body or cells. Macrophages are also believed to "clean house" in your body. These cells get cleared of cells that are worn out and need to be repaired. Macrophages also perform a role in wound healing and limb recovery.

The macrophage plays a significant role in both the innate and acquired (humoral and cellular) immune responses. The macrophages will remain for several months after they are produced.

The method of the macrophage surrounding, covering and killing foreign bodies is called phagocytosis. It comes from the Greek words "phagein" intending to eat, "kytos" or cell and "osis" which means process.

Importantly, the macrophages can recognize self from non-self so that they do not hurt or destroy cells of normal appearance or function.

Innate immunity

Everyone is born with innate (or natural) immunity, a kind of universal protection. For instance, the skin serves as a wall to block bacteria from accessing the body. And the immune system identifies when some invaders are foreign and could be deadly.

Adaptive immunity

Adaptive (or active) immunity extends throughout our lives. We generate adaptive immunity when we're opened to diseases or when we're immunized on them with vaccines.

Passive immunity

Passive immunity is "borrowed" from a different source and it serves for a short time. For instance, antibodies in a mother's breast milk supply a baby temporary immunity to illnesses the mother has been endangered too.