What is Immunity? A Guide to How the Immune System Works

Dr. Rajkumar Vinod Desai

Medically reviewed by

Dr. Rajkumar Vinod Desai

General Physician

4 min read

Key Takeaways

  • Immunity is the ability of the body to prevent the entry of a pathogen
  • Innate, adaptive and passive are the three types of immunity
  • White blood cells play a key role in the immune system working process

The immune system is vital for our survival. Without it, the body is susceptible to disease-causing microorganisms. It is solely because of our immunity that we can fight and prevent foreign bodies from attacking us. A foreign substance could be any pathogen, including viruses, bacteria, protozoa, or even parasites.

A complex network of cells and proteins, the immune system keeps track of different pathogens entering the body. When the same organism reenters, it can recognize and destroy them. Read on to know what immunity is and learn more about the immune system working process.

What is immunity? 

The ability of your body to resist an invasion by pathogens is called immunity. These pathogens contain antigens on their surface. They elicit an immune response upon entering the body. This immune response is the body’s defense mechanism to fight against these pathogens.

Additional Read: Important Symptoms of Weak Immunity and How to Improve It

What are the components of the immune system? 

An immune system comprises the following components.

  • White blood cells or WBCs, also known as leukocytes, circulate throughout the body in the blood and lymphatic vessels. These play an important role in the functioning of the immune system<span data-contrast="auto"> by constantly checking if any pathogen has invaded the body. On locating a pathogen, these cells multiply and signal other cells. WBCs are stored in lymphoid organs, namely the thymus, spleen, lymph nodes, and bone marrow.
  • You can find two main types of leukocytes in the body, which are phagocytes and lymphocytes.

Phagocytes function by absorbing and eating the pathogen. There are different types of phagocytes that include the following.

  • Neutrophils
  • Monocytes
  • Mast cells
  • Macrophages

Lymphocytes are the cells that help the body to recognize if the pathogen has previously invaded it or not. Produced in the bone marrow, they are classified as B-cells and T-cells. Lymphocytes staying in the bone marrow are B-cells and the ones migrating to the thymus are T-cells. B-cells produce antibodies while sending alert signals to T-cells. T-cells function by destroying the affected cells and alerting other leukocytes. [1]

active and passive immunity

What are the types of immunity? 

There are three types of immunity: innate, adaptive, and passive immunity.

Innate immunity is the body’s first line of defense. It is the protection present in your body right from birth. It includes barriers such as mucous membranes and skin. Often referred to as non-specific immunity, these barriers prevent the entry of pathogens into the body.

Adaptive immunity or active immunity happens when your body is exposed to a disease-causing organism. Consequently, the body produces antibodies. The next time the same pathogen invades, the body fights it off with those antibodies. Apart from this, vaccination can also result in developing adaptive immunity.

Passive immunity happens when you have antibodies already present in the immune system. A newborn baby acquires passive immunity from the mother via the placenta. The most crucial factor to consider when differentiating between active and passive immunity<span data-contrast="auto"> is that the former is permanent and long-lasting. Passive immunity is temporary. [2]

How the immune system works 

As it is clear, the body can clearly distinguish self from non-self. The immune system strives hard to get rid of pathogens that have invaded the body. Upon recognition, B-cells are triggered to produce antibodies that can lock specific antigens. These antibodies cannot kill antigens without the help of T-cells. T-cells identify antibody-locked antigens and send out an alert signal to other leukocytes like phagocytes, killing these cells. How immunity works in your body is solely dependent on the immune response sparked by the antigen. [3]

Tips to improve immunity 

The first and foremost way to improve immunity is to follow an active and healthy lifestyle by incorporating the following essential tips. 

  • Exercise regularly 
  • Consume a diet rich in vegetables and fruits 
  • Keep a check on your body weight
  • Ensure you have a healthy sleeping pattern
  • Try to reduce stress with meditation and other stressbusters
  • Avoid junk food
Additional read: Boost Your Immunity with This Healthy and Nutritious Indian Meal Plan

Now that you know what immunity is, you can understand the mechanism and workings of the immune system are complex processes. Anything gone wrong can lead to serious disorders. These include hypersensitivity if the immune system overreacts, immunodeficiencies when it underreacts, and autoimmune disorders when it fails to distinguish its own cells from foreign bodies. If you face symptoms related to any of the above, book an in-person or online doctor consultation on Bajaj Finserv Health. Connect with specialists near you within minutes and ensure you give your health the attention it deserves.

Published on 3 Aug 2021Last updated on 5 Apr 2023
  1. https://kidshealth.org/en/parents/immune.html
  2. https://www.medicalnewstoday.com/articles/320101#immune-system-disorders
  3. https://www.ncbi.nlm.nih.gov/books/NBK279364/

Please note that this article is solely meant for informational purposes and Bajaj Finserv Health Limited (“BFHL”) does not shoulder any responsibility of the views/advice/information expressed/given by the writer/reviewer/originator. This article should not be considered as a substitute for any medical advice, diagnosis or treatment. Always consult with your trusted physician/qualified healthcare professional to evaluate your medical condition. The above article has been reviewed by a qualified doctor and BFHL is not responsible for any damages for any information or services provided by any third party.

Dr. Rajkumar Vinod Desai

Medically reviewed by

Dr. Rajkumar Vinod Desai

, MBBS 1


Health Videos

Mobile Frame
Download our app

Download the Bajaj Health App

Stay Up-to-date with Health Trends. Read latest blogs on health and wellness. Know More!

Get the link to download the app

Google PlayApp store