What Is the Immune System?
What Does Your Immune System Do?
The immune system protects you from infections by viruses, bacteria, fungi, and parasites.
What Is Your Immune System Made Up Of?
The immune system is made up of a combination of many organs, specialized proteins, white blood cells, and antibodies.
Organs of the Immune System
Several organ systems are involved in the functions of the immune system. Careful coordination and regulation of these organs are required to keep the immune system working optimally.
Skin: Many people don't think of it, but your skin is actually one of the most important organs of the immune system. Skin acts as a barrier to keep potential invaders from entering the body. Acids found in sweat help by making the skin inhospitable to bacteria. The bacteria that naturally live on your skin can also be useful. They produce toxins to keep competing bacteria from entering their territory.
Lymphatic System: The lymphatic system is another vital part of the immune system. It consists of a series of ducts and capillaries that connect the various lymph nodes and lymphoid organs spread throughout the body. Unlike the circulatory system, where blood is pumped by the heart, the lymphatic system is passive. It moves fluid, fat, and white blood cells throughout the body.
Thymus: The thymus is an organ located close to the hearth. This is where T-cells mature. Lymphocyte precursors, produced in the bone marrow, migrate to the thymus, where they turn into thymocytes and eventually, T-cells. Most of this process takes place early in life, so the thymus is not particularly important in adults.
Adenoids: Like the thymus, the adenoids become less important over time. They are located at the back of the nose and help prevent infections from inhaled antigens. The Adenoids are large in childhood, but quickly atrophy during the teenage years.
Tonsils: The tonsils are located at the back of the throat and help fight off upper respiratory tract infections. Like the adenoids, they tend to shrink and become less effective with time, although doctors still recommend that you not have them removed unless necessary since they do still contribute somewhat to the functioning of the immune system.
Spleen: Located in the abdomen, the spleen has two main functions: to filter blood for foreign particles and dying red blood cells and to coordinate the immune response. While the spleen can be removed without serious consequences, the loss of this organ does leave you more open to septic infections.
Bone Marrow: The final organ of the immune system is the bone marrow. The bone marrow produces the precursors for white blood cells, including those of both the T-cells and B-cells, as well as the red blood cells and platelets.
The Complement System
The complement system is made up of circulating proteins. Most of the time, these proteins lie dormant, but when an antigen enters the body, they become active. The complement system releases chemicals that make the vascular system more permeable to white blood cells. It also releases cytokines (chemical communicators) to summon phagocytes, and, in some cases, works with antibodies to destroy antigens.
White Blood Cells
White blood cells are essential to the immune response. There are a few different categories of white blood cells that are especially important:
- Phagocytes - These cells engulf antigens and destroy them.
- T-cells - T-cells help modulate the immune response.
- B-cells - The B-cell produce antibodies specific to a particular antigen.
Antibodies are the final and most refined components of the immune system. They have binding sites specific to a certain antigen. When they encounter the antigen, they attach themselves, thereby making the antigen easy for the rest of the immune system to identify and attack. In some cases, antibodies themselves contribute to the demise of invading pathogens.