The Immune System: How It Works (2 of 4)


For a long time, science didn’t pay much attention to the immune system, but that is now swiftly changing. In this 2nd article, we highlight the new understanding of how the immune system works, particularly in detecting and responding to threats.

immune systemThe immune system mainly functions through a highly specialised group of cells that travel to every nook and cranny of our body through our blood and lymphatic system. These cells are produced, schooled and harboured in the bone marrow, thymus gland, lymph glands and spleen.

Sensitive & Powerful

To do their job effectively, immune cells have to be

  • Sensitive:  they are exquisitely calibrated to detect and differentiate what is ‘self’ (to be left alone) and ‘non-self’ (to be neutralised).
  • Powerful: they are also a specialised, potent and comprehensive arsenal of all that is needed to deal with the ‘non-self’ agents.

Detection & Action

The method of detection is through ‘antigens’: distinctive molecules on the surface of non-self cells, which the patrolling immune cell recognises as ‘foreign’. Immediately the immune cell does two things:

  • One, it provides the antidote in the form of an antibody protein that perfectly fits into the antigen, like a key to lock it or turn it off.
  • Two, as soon as the intruder is locked-in or pinned down, it sends out a call to arms to its roving compatriots through bio-chemical messengers, who in turn, launch a cascade of immunological reactions called the immune response.

immune response: antigen triggering release of antibodies

Immune Response

There are many kinds of immune responses, depending on the situation.

Inflammation is one such. When tissues are injured or damaged, the immune system releases chemicals that cause blood vessels to leak fluid into the tissues, causing swelling. This swelling helps isolate the foreign substance from further contact with body tissues. The same chemicals also attract white blood cells called phagocytes. They surround, engulf and ultimately digest foreign cells. This process is called phagocytosis.

Other immune responses include

  • Producing more immune cells or more antibodies if required
  • Injecting the foreign body with toxins or puncturing its membrane to dissolve it.
  • Some immune cells (called macrophages) act as garbage collectors and they clean up the debris after the battle is over.
  • There are even suppressor cells that signal when it is time to ‘call off’ the attack or stop the immune response.
  • Finally, the immune system also records and stores the signature characteristic of every new antigen it encounters, so it can launch an even swifter counter-attack should the same antigen appear again.


  • How does your body react when it is ill, as compared to when it is well?
  • What typical signals does your body send you, which point to a weak or compromised immunity?
  • Knowing that your immune system is always supporting you, what steps can you take, to keep it in optimum condition?

More from this series

Title About the article
A Little Known Marvel While there exist innumerable disease agents inside and outside of us (bacteria, viruses, toxins, cancer cells etc.), nature has also provided us with an in-built defence system which is constantly at work.
How It Works The immune system mainly functions through a highly specialised group of cells that travel to every nook and cranny of our body through our blood and lymphatic system.
Dealing With Cancer According to available research, an average person typically has around 70 cell mutations in their lifetime. Any one of these mutations could lead to cancer … and yet, a large majority of them don’t.
Mind Body Bridge Until recently, medical science considered the immune system to be an independent, self-regulatory system.



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