How Your Immune System Works

What is the immune system and how does it work?

The immune system is regarded as the natural defense system in your body. The immune system, together with a network of cells and tissues, as well as body organs, protects your body against harmful foreign invaders or substances. Examples of foreign invaders are viruses, bacteria, fungi, and parasites. 

What is immunity?

Immunity is the protection of our body from various external and internal invaders attacking our body. We are surrounded with viruses, bacteria, parasites and fungi in our daily life, however, they do not normally attack us unless our body becomes weaker due to certain circumstances.

Moreover, our body hosts some normal flora (bacteria) that are useful for our digestion. They live in the gut, helping us to get all the useful substances from the food we eat.

When a person has a strong immune system, foreign invaders are stopped through the system’s network of barriers. However, if the barriers become vulnerable, the immune system responds by producing white blood cells (WBCs) and other chemicals in the body to destroy the foreign invaders. 

Cellular blood consists of red blood cells (RBCs), white blood cells (WBCs), and platelets. The red blood cells or erythrocytes are responsible for the nourishment of all tissues with oxygen, while the white blood cells or leukocytes function as fighters against different types of infections. With regards to immunity, the leukocytes play a major role. Specific types of leukocytes are involved in a person's immunity, and they include T lymphocytes, B lymphocytes, and macrophages (large phagocytic cells).

• Macrophages - the macrophages in our body look for foreign bodies and ingest them. They undergo a process of phagocytosis to consume the particles and then digest them. These particles are called antigens. Our immune system identifies these antigens as foreign substances and tries to get rid of it. After phagocytosis, the phagocytes die and pus is formed from the collection of dead tissues, bacteria, and other alive or dead phagocytes.
• B lymphocytes - are the ones that produce the antibodies that attack and clean up the antigen left behind by the macrophages. 
• T lymphocytes - attack cells that are already infected.

Our body has a clever system. Our blood contains memory cells that carry some information about the antigens. Thus, the next time a harmful organism attacks our body, the immune system sends a signal to the B lymphocytes to produce specific antibodies to fight the bug. Sometimes, it takes up to 7-10 days to fight the infection and prevent the development of the disease. This fact explains how an individual's immunity works. However, some of the immune responses are not stable and can wear out. For this reason, an artificial immunization is needed for the prevention of deadly diseases, especially in children. Although artificial, vaccination is still the most appropriate method in boosting overall body immunity.

Inflammation

When tissues in the body are damaged by harmful microorganisms or injured by trauma, heat and certain toxic substances, an inflammatory response occurs. The tissues or cells that are damaged release specific chemicals such as histamine, prostaglandins, and bradykinin, which cause the blood vessels to leak into the tissues. This leaking causes swelling, which helps separate the foreign particles with the body’s tissues.

Where is the immune system located in our body?

The lymphatic system plays an essential role in our body's defense system (immune system). It consists of bone marrow, spleen, thymus, and lymph nodes.

• Thymus - is an organ that is located in the mediastinum and is the place where T cells mature. They help destroy infected or cancerous cells, which may appear due to the mutations and exposure to some hazardous substances.
• Bone marrow - is the matrix of all blood cells since it produces all blood cells in the body.
• Spleen - is the largest lymphatic organ in the body that contains white blood cells (WBCs), which combat infections. The spleen is the organ where white blood cells (WBCs) are stored and the place where the red blood cells (RBCs) are destroyed.
• Lymph nodes - are glands that are found in the neck. It filters lymph, which is the fluid that circulates through the body's lymphatic system. The enlargement of lymph nodes is a distinguishing factor for an acute infection. Depending on the location of the enlarged lymph nodes, doctors can establish a primary diagnosis of the disease and its causative factor. For example, if a person has rubella or German measles, usually, the lymph nodes found at the back of our neck get enlarged. 

Types of Immunity

Humans have two types of immunity: congenital (inborn) and artificial (obtained through vaccinations). 

• Congenital immunity - is a type of immunity that is present at birth. Congenital immunity can either be natural or acquired. An acquired immunity happens when a newborn child receives the mother’s antibodies through the placenta. 
• Vaccination - is an efficient way of artificial immunization. For example, we are not born resistant to tetanus, so it is vital to get immunized against it, especially for those people whose are frequently exposed to injuries or trauma.

How does the immune system respond?

The immune system is like a guardian that keeps the body free from harm. When the body is attacked by infectious microorganisms such as viruses and bacteria, or if there are abnormal cellular growths, certain allergens, and other external factors that alter the body's normal system, the immune system quickly recognizes them and starts acting upon them.

Antigens signal the immune system as they begin binding themselves to cell receptors. The immune system attempts to restore a state of normalcy. While pathogenic substances are attacked by the responses of the innate immune system, some antibodies attack deadly pathogens via learned responses through the adaptive immune system. Either acquired or learned, the immune system immediately responds to any pathogens that harm the body. Vaccinations, shots, and boosters can be administered every now and then for children, and as recommended by doctors for adults. Vaccinations have proven to be essential for keeping the body's immune system strong and healthy.