What is an Immune System & Their Types?

What is an immune system?

The immune system is a complex network of cells and proteins that protects the body against the infection. Without an immune system, the bacteria, viruses, parasites, etc can easily attack our bodies. The immune system is made up of special organs and cells that fight microbial infection. The immune system comprises white blood cells, antibodies, lymphatic Systems, compliment system, spleen, thymus and bone marrow. These all actively fight infection together.
The immune system is spread throughout the body. It can easily identify the foreign tissues; basically, it can distinguish between self and non-self. It can also recognize and clear the dead cells.

Types of immunity

There are mainly three types of immunity in human that are innate, adaptive and passive immunity:

  • Innate immunity
    All human beings are born with some level of immunity. Innate immunity includes the external barriers of the body such as skin and mucous membranes of the throat and gut which acts as the first line of defense. This response is more general and non-specific. Even through this if the pathogens enter the body, then the adaptive immunity kicks in.
  • Adaptive/ acquired immunity
    As we grow, this acquired immunity develops and protects us from the pathogen and is highly specific. When we get vaccinated, our body maintains an immunological memory against the pathogens. Acquired immunity provides long-lasting protection from the invaders, for example, chickenpox. Memory cells in the body remain ready to respond rapidly if the same pathogen attacks the body.
  • Passive immunity
    This type of immunity is adapted from another body. For instance, a baby receives antibodies from the mother through the placenta in the womb and from the breast milk after birth. This passive immunity protects the child from infections during the early years of life.

What are the main components of the immune system

Lymph nodes

Lymph nodes are the kidney-shaped organs of the lymphatic system. They are distributed throughout the body. Lymph nodes are the main sites for B and T cells and WBCs. They swell in various diseases, which can be life-threatening also. Their primary function is the filtering of lymph to identify and fight infections.


It is the largest lymphatic organ in the body. It is located on the left side, of the body under the rib cage. It contains white blood cells that defend the body from infection. It also plays a major role in the recycling of old red blood cells, while stores platelets and white blood cells.

Bone marrow

Bone marrow is a spongy and flexible tissue inside the bones that contains stem cells. These stem cells develop into red blood cells and carry oxygen through the body. It also removes old cells from the blood. The hematopoietic stem cells are responsible for the production of blood cells such as white blood cells and platelets.


The thymus gland is a small organ situated beneath the breastbone. The thymus is the maturing site for T-cells. It is usually large in infants and starts to shrink slowly with age after puberty.


Lymphocytes originate in the bone marrow. There are 2 types of cells which have different roles:

  • B lymphocytes: They secrete antibodies and are found in blood, lymph nodes, spleen, tonsils and mucosal tissues.
  • T lymphocytes: T cells develop in the thymus gland and play a significant role in the immune response. In the thymus, these cells multiply and differentiate into helper, regulatory and memory T cells. These cells help to protect the body from infection.

White blood cells (WBCs)

They are also called leukocytes. They are spread all over the body in blood vessels and lymphatic vessels. When the WBCs find a target they began to multiply and send the signals to other cells for performing the same function.

How the immune system is activated?

It can be activated by the different things which our body doesn’t recognize. These particles are called antigens. These antigens could be bacteria, viruses or fungi. When these antigens attach to the receptors on immune system cells, many processes are activated in our bodies. When the body came in contact with these germs, it usually makes the memory cells against the germs. The microorganisms that cross the mechanical, chemical and biological barriers of our body trigger the immunological responses in a coordinated way.

How to improve the immune system?

Your immune system does an outstanding job of protecting you against disease-causing microorganisms. But sometimes it could be weakened; a microorganism can enter your body and make you sick. That’s why some people become ill very often. For now, there are no scientifically proven links between the lifestyle and increased immunity, while on the behalf of evidence here is the idea to boost immunity.

Following health-guidelines can help you to naturally keeping your immune system stronger:

  • Quit smoking: It can increase the risk of cancer and it reduces the effectiveness of the immune system’s defense.
  • Moderate intake of alcohol: excessive intake of alcohol can alter with immune pathways. While according to the studies moderate intake of alcohol can be helpful for the body.
  • Eating a healthy diet: vegetables, fruits, legumes, cereals are loaded with nutrients and can boost the immune system when consumed daily.
  • Exercise regularly: Regular exercises can activate the T cells.
    Maintaining a healthy weight: Obesity can be the reason for various chronic diseases.
  • Get enough sleep: Lack of sleep can cause an inflammatory immune response. Try to sleep for about 6-8 hours minimum.
  • Maintain personal hygiene: Wash your hands before cooking and eating as hands can be the source of microorganisms.
  • Avoid stressful activities: Chronic stress decreases the efficiency of the immune system by releasing the cortisol hormone which reduces the antibody secretion.
  • Step out in sun: Natural sunlight is the source of vitamin D to our body which helps the body to produce antibodies.
  • Start consuming mushrooms: Mushrooms are one of the healthiest foods in the world. Some of the mushrooms like Turkey tail, Tremella and Maitake Mushrooms are good for the immune system.

With these natural ways, you can boost your immune system and achieve a healthy lifestyle. Stronger the immune system, the lesser will be the chance of falling ill.


Deepa Mahar is a content writer who is exploring the beauty of the blog writing from a variety of subjects and books to health, science and others. Her article focuses on information and research about the immune system. She believes the blog would be helpful to the reader in the context of knowledge. She is admin of DeepAdvices

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