The immune system is the one in charge to protect the body against viral bacteria and invading microorganisms. It protects the body through a series of steps called the immune response. So, basically, the immune system attacks any organisms and substances that can possibly harm the human body. 

An immune system is composed of a series of network cells, organs, and tissues that work together to protect the body. One of the most important cells involved is the white blood cells, or what doctors call the leukocytes

The leukocytes are found in many locations of the body. These locations include the spleen, thymus, and bone marrow. For this reason, they are called lymphoid organs. Inside the body, there are clumps of lymphoid tissue or what they call as the lymph nodes. It primarily houses the leukocytes in the body. 

Leukocytes circulate between the nodes and organs through blood vessels and lymphatic vessels. This way, the immune system works in an organized manner to check if the body has bacteria and substances that might cause problems.

The main components of the immune system are the tonsils, thymus, lymphatic system, bone marrow, spleen, and white blood cells. 

The Thymus

The thymus or thymus gland can only fully developed in children and it will turn into a fat tissue from adolescence onwards. You can locate the thymus gland behind the breast bone but slightly above the heart. Particular defense cells like T lymphocytes or T cells for short are situated on the thymus gland. These T cells are responsible for coordinating the innate and adaptive immune system

The letter “T” in T lymphocytes or T cells stands for thymus, where they can be located and the place where they mature inside the body. The T cells constantly move through the body to watch the surfaces of all the cells for changes. For these types of cells to do their job, they learned while in the thymus which structures are non-self and self in the cell surface. 

When T lymphocytes come in contact with a non-self body, these cells turn into T effector cells that regulate various defense reactions. In addition to that, these cells also produce T killer cells, which helps fight a pathogen. There are also T helper cells, another kind of effector cells that helps other immune cells in doing their job

The Tonsils

The tonsils or palatine tonsils are located at the pharynx or at the rear of the throat. It’s a pair of soft tissue similar to lymph nodes, covered by pink mucosa (like on the adjacent mouth lining). In line with the mucosa are pits for each tonsil. These pits are called crypts.

These soft tissues or the tonsils are part of the lymphatic system, which helps the body fight infections. It may look large in children, but the size of the tonsils tend to get smaller when the person becomes an adult. Though tonsils seem useless, they are still quite helpful to the human body. 

One of the primary functions of palatine tonsils is that they prevent foreign objects from slipping into the lungs when a person is eating. They also produce antibodies and white blood cells, which enables them to filter bacteria and viruses. 

Lymphatic System 

The lymphatic system is built up of lymph nodes. These nodes are tiny, kidney-shaped organs discovered throughout our lives. The human body has up to 600 lymph nodes. They produce lymph fluid from the lymph system, which is packed with lymphocytes. 

These lymphocytes are like white blood cells which help the body fight bacteria and viruses. Lymph layers serve as filters to clean the lymphatic fluid. It functions by activating the white blood cells to kill the attackers.

Bone Marrow

One of the primary components of the immune system is the bone marrow. The bone marrow is a soft tissue that can be found in the long bones of the fingers, ankles, vertebrae and pelvic bones. It’s a gelatinous tissue the fills the medullary cavities or the centers of bones. There are two different types of bone marrow. The red bone marrow which is known as myeloid tissue, and the yellow bone marrow or the fatty tissue. 

Red and yellow bone marrow are packed with capillaries and blood vessels. The red bone marrow produces most of the red blood cells needed by the body and 60 to 70 percent of it is lymphocytes. Some special white blood cells of lymphocytes begin life in the red bone marrow but become fully formed in the lymphatic tissues. Also one of the functions of the red bone marrow is to get rid of the old red blood cells produced by the body. 

The yellow bone marrow primarily acts as a storage for fats. One of its functions is to provide sustenance and maintain the right environment for the bone to function. However, under certain conditions such as fever or severe blood loss, the yellow bone marrow may become a red marrow. 


The Spleen is an organ in the abdominal cavity’s right hand. In addition to that, the spleen consists of more than half of the body’s monocytes, a special type of white blood cell. It can also house 1/4 of the body’s lymphocytes. One function of the spleen is to destroy old red blood cells that have achieved the completion of their life cycle, collecting, and processing blood. 

The spleen is an essential organ for the immune system response. Removing your spleen increases the risk of having infections and other related diseases. Moreover, if a spleen doesn’t function properly, it may bring harm to the function of the B cell, a type of white blood cell. It can also disrupt the good function of white blood cells.

White blood Cells

White blood cells are created by the bone marrow to protect your body against infections and diseases. These cells react to protect the body if an infection forms such as bacterias, allergens, and viruses. 

All the cells inside of our body are working on fighting all the bacterias. Also, white blood cells are known as leukocytes,  and they act independently inside the human body.

There are four types of immunity:

Innate Immunity

Innate immunity is your natural defense mechanism and keeps you safe from all antigens. This type of immunity have barriers that prevent the body from acquiring harmful bacteria and viruses. The first row of protection in the immune response is these barriers. 

Natural strength elements such as untouched hair, salivary proteins, intact skin, neutrophils, and innate killer neurons react to a disease before the body is introduced to a virus or antigen. This type of immunity is the first to detect when an organism does not belong to the body and directs the adaptive part to tackle the intruder. 

Adaptive Immune System

The adaptive immune system, also known as the acquired immune system is a subsystem of the overall immune system. It’s sometimes called the specific immune system composed of systematic cells that are highly specialized to eliminate pathogens or to prevent their growth

Active Immunity

Active immunity is a technique by which the body is to produce an adaptive immune response when exposed to an antigen. It lasts days/weeks to create the reaction, but it can last for a long time. 

For instance, hepatitis-A virus restoration provides an innate effective immune response that generally leads to permanent safety. Similarly, two-dose Hepatitis-A vaccine administration produces a gained effective immune response that leads to long-lasting protection.

Passive Immunity

Passive immunity is caused by antibodies in a body other than yours. Babies have passive immunity because they are conceived with antibodies transmitted from their mom through the placenta. However, these antibodies vanish from 6 to 12 months of age. 

Passive immunization may also be caused by antiserum injection, which are antibodies created by another individual or animal. It offers instant security from an antigen but does not provide long-term security. Examples of passive immunization include immune serum globulin (provided for access to tuberculosis) and tetanus antitoxin.


Understanding the immune system takes years to study, but seconds to destroy. Therefore, to have a healthy immune system, you need to take care of your body. Having a healthy body means having a strong immune system. The immune system continues to grow and develop inside the human body. So as long as you live, it’ll continue to protect you from harmful diseases and viruses.