What is immune system??

Hello everybody,

These days we are listening the word “IMMUNITY” many times. You might have seen immunebooster drinks, immunity bread and many such products in advertisements. So, what does this word actually mean? Let me help you to understand the word immunity, its types, how to build immunity, and disorders related to it.


Immune system is a complex organization that recognize and tolerate the self and reject the foreign particles. In simpler words it is a check point, acts like body’s defense against infections.

Many cells and organs work together to build this immune system. Phagocytes, lymphocytes, neutrophils , these names you would have come across in blood report. These are the cells of immune system.

Humans have three kinds of immunity:

 Innate immunity : Everyone is born with innate immunity. For example : skin acts like a barrier for germs.

Adaptive immunity: This immunity is developed whenever we contract diseases or vaccinated against some disease. For example: polio vaccine.

Passive immunity: It is borrowed immunity and lasts for shorter duration. For example: Mother contracted by some disease during pregnancy gives immunity to her baby for short period of time.

Body fights against many diseases by producing antibodies. Above mentioned three types work together in fighting diseases.


  • Antigen recognition: In our body we have HLA present on our cells which acts as ID of self cells. The cells which don’t have HLA are treated as foreign and immune system recognizes it as antigen.
  • Bone marrow: It is the place where immune cells are manufactured.
  • Phagocytes: These are part of innate immunity and act by eating foreign particles.

1) Neutrophils: They will respond first to infection by eating bad cells and preventing bacteria infection.

2) Macrophages: They work in eliminating bacterial infection from tissues.

3) Eosinophils: These attack and kill big antigens by attaching to them.

  • Natural killer cells: They mainly attack abnormal cells like cancer cells. These have a major role during viral infection.
  • Lymphocytes : T and B are the main lymphocytes are the main cells to build acquired immunity.

These are some of the important players of immune system.


Each B-cell makes specific antibody whenever they encounter the antigen.

Antibodies are part of large group of chemicals called immunoglobulins.

1) IgM: kills bacteria

2) IgD: helps B cells in starting the immune response

3) IgA: present in tears and saliva, prevent antigen entry

4) IgG: it tags the antigen so that it is recognised by immune cells as antigen

5) IgE: protect against parasites and acts during allergies


1) Helper T-cells( TH): These cells stimulate B cells to produce more antibodies. Others attract more T cells or cell-eating phagocytes.

2) Killer T-cells ( TC): These play main role in fighting viruses. These identify specific patterns on the surface of viruses and destroy them.

Diseases related to immune system and why do they occur:

When immune system does not work properly it results in various disorders. Reasons for this may be primary immune deficiency i.e born with weak immune, Hyper active immune system due to allergies, acquired immune deficiency syndrome, and auto immune disorder.

  • Severe combined immunodeficiency (SCID): Children are in constant danger of infections from bacteria, viruses, and fungi, and the disorder is called “bubble boy disease.” In the 1970s, a boy had to live in a sterile environment inside a plastic bubble. It is primary immune deficiency.
  • Acquired immune  deficiency : Immune system can be weakened by certain medicines, for example. This can happen to people on chemotherapy or other drugs used to treat cancer. It can also happen to people following organ transplants who take medicine to prevent organ rejection. Infections like the flu virus,and measles can weaken the immune system.Immune system can also be weakened by smoking, alcohol, and poor nutrition.
  • AIDS. HIV, which causes AIDS, is an acquired viral infection that destroys important white blood cells and weakens the immune system. These diseases take advantage of weak immune system.
  • Hyperactive immune system: For some people the factors in environment may act as allergens like pollens, dust, and food items.Some diseases are caused by overactive response of immune system:
  • Asthma : In  lungs, it can cause coughing, wheezing, and trouble breathing. Asthma can be triggered by common allergens like dust or pollen or by an irritant like tobacco smoke.
  • Eczema.:An allergen causes an itchy rash known as atopic dermatitis.
  • Allergic rhinitis: Sneezing, a runny nose, sniffling, and swelling of your nasal passages from indoor allergens like dust and pets or outdoor allergens like pollens or molds.

Autoimmune disorders: In autoimmune diseases, the body attacks normal, healthy tissues and is probably a collection of a person’s genes and something in the environment that triggers genes.

  • Type 1 diabetes: The immune system attacks the cells in the pancreas that make insulin. Insulin removes sugar from the blood to use as energy.
  • Rheumatoid arthritis: It causes swelling and deformities of the joints. An auto-antibody called rheumatoid factor is in the blood of some people with rheumatoid arthritis.
  • Lupus: It attacks body tissues, including the lungs, kidneys, and skin. Many types of auto-antibodies are found in the blood of people with lupus.

Even Graves and Celiac diseases come under auto immune diseases.


Building immunity means building white blood cells. This can be achieved by various methods like-

1) Eat more plant foods: Whole plant foods like fruits, vegetables, nuts, seeds, and legumes are rich in nutrients and antioxidants that may give you an upper hand against harmful pathogens.

2) Eat more healthy fats: By this I mean include olive oil, salmon and chia seeds in your diet.

3) Eat fermented foods: Fermented foods are rich in beneficial bacteria called probiotics. These foods include yogurt, sauerkraut, kimchi, kefir, and natto. These help to identify and target harmful pathogens.

4)Physical exercise: Examples of moderate exercise include walking,steady bicycling, jogging, swimming, and light hiking. Most people should aim for at least 150 minutes of moderate exercise per week.

Hope you guys got a clear idea of immunity.

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