Immune System

  • We say that there are millions of micro organisms and germs that we can’t see with our naked eyes. But how do we not get sick every time our body comes in contact with some germs?
  • Why is it that some people enjoy spring, but a few others fall sick at the same time? Let us understand this with the help of a story.



Once upon a time, there was an island (human body) named after the queen, Marcela. She took good care of everyone living on the island. They ate healthy food every day like apples, spinach etc. Then one day, four pirate germ ships came to the island to invade it. The first ship had viruses, which live in living cells and cause diseases like the flu, common cold.

The second ship had fungi, microscopic organisms that cause itchy rashes. The third ship had parasites, which can cause diarrhoea and other problems. And the last ship had pirates called as bacteria, which are one-celled microbes which can cause infections like pneumonia and food poisoning.

The queen had warned the habitats that not all germ pirates living among them were bad, some helped the island a lot, but there were other bad germ pirates which caused diseases and wanted to destroy the island.

Queen Marcela immediately called a meeting of her trusted advisors. There was Vaccine, Hand-o-fingers, Apple Mcdietson, Runnylegs and Snoozer. Upon asking about their advice, vaccine said that the island could have taken preventive measures, by taking vaccines, which is called as immunisation.

This help prevents bad illnesses such as whooping cough, tetanus and the flu. After getting the vaccine, the body is more protected. Hands said that washing one’s hands regularly will help prevent invasion by the germs. Apple contributed to the discussion by saying that everyone should eat nutritious food daily and started singing “an apple a day, keeps the doctor away”.

Runny legs said to get enough exercise, run, jump, dance, whatever gets you moving. Snoozer said to get a good amount of sleep. Despite the best efforts, sometimes the germs can still invade our body; and the same was happening to the island.

Looking at the worsening situation, Queen Marcela assembled the immune system knights – Leukocytes– commonly called as the white blood cells (WBCs).

White Blood Cells

These play an essential role by continually scanning the tissues and organs for any suspicious signs. These cells remember the diseases and the germs that had attacked the body before. Hence, these leukocytes fought against the germ pirates and the island was saved. 

  • This high tech, the advanced defence system is called the immune system. This immune system protects you from all the unwanted guests keeping you safe and healthy.
  • This system isn’t just a part of the body, but a collection and collective work of tissues, cells and organs. These include lymph nodes, lymphocytes, lymph vessels, bone marrow, skin and much more.
  • As soon as the leukocytes detect that the body has been infected by antigens, lymphocytes are activated. The T-lymphocytes search the infected cells and destroy them, whereas, the B- lymphocytes produce antibodies.

Important Words

Antibodies– These are special proteins which lock on to the antigens and destroy them protecting from further infection.

Antigens– These are foreign substances (because they are unknown to the body), which infect the body and lead to the production of the immune response.

  • While this is all happening inside your body, you will develop symptoms like high fever, to help your body fight off the germs. This is because bacteria and virus find it hard to multiply under high temperatures.

FUN FACT: Did you know that allergies are the result of your immune system reacting to a false alarm !!


Let’s have a quick quiz to see how confident you are about the topic now:

1. Getting vaccines leads to

  1. Stronger immune system
  2. Immunisation
  3. Both a and b
  4. None of the above

2. Antigens are produced due to the attack of antibodies

  1. True
  2. False

3. Antibodies have the ability to recognise older diseases and germs

  1. True
  2. False

4. Which of the following should be avoided to have a healthy immune system?

  1. Apples
  2. Playing
  3. Junk food
  4. Water

5. Which cells help destroy infected cells?

  1. T-lymphocytes
  2. Red Blood Cells
  3. Both a and b
  4. None of the above

Related Articles


For Worksheets & PrintablesJoin Now