The role of the immune system is to protect against disease or other potentially damaging foreign bodies. When functioning properly, the immune system identifies a variety of threats, including viruses, bacteria and parasites, and distinguishes them from the body's own healthy tissue, according to Merck Manuals.
The major components of the immune system:
- • Lymph nodes: Small, bean-shaped structures that produce and store cells that fight infection and disease and are part of the lymphatic system — which consists of bone marrow, spleen, thymus and lymph nodes.
- • Spleen: The largest lymphatic organ in the body, which is on your left side, under your ribs and above your stomach, contains white blood cells that fight infection or disease.
- • Bone marrow: The yellow tissue in the center of the bones produces white blood cells. This spongy tissue inside some bones, such as the hip and thigh bones contains immature cells, called stem cells, according to the NIH.
- • Lymphocytes: These small white blood cells play a large role in defending the body against disease.. The two types of lymphocytes are B-cells, which make antibodies that attack bacteria and toxins, and T-cells, which help destroy infected or cancerous cells. Killer T-cells are a subgroup of T-cells that kill cells that are infected with viruses and other pathogens or are otherwise damaged.
- • Thymus: This small organ is where T-cells mature. This often-overlooked part of the immune system, which is situated beneath the breastbone (and is shaped like a thyme leaf, hence the name), can trigger or maintain the production of antibodies that can result in muscle weakness, the Mayo Clinic said. Interestingly, the thymus is somewhat large in infants, grows until puberty, then starts to slowly shrink and become replaced by fat with age.
- • Leukocytes: These disease-fighting white blood cells identify and eliminate pathogens and are the second arm of the innate immune system. A high white blood cell count is referred to as leukocytosis.
Diseases of the immune system:
If immune system-related diseases are defined very broadly, then allergic diseases such as allergic rhinitis, asthma, and eczema are very common. Asthma and allergies also involve the immune system. A normally harmless material, such as grass pollen, food particles, mold or pet dander, is mistaken for a severe threat and attacked. Other deregulations of the immune system includes autoimmune diseases such as lupus and rheumatoid arthritis.