The Prologue

A human body co-exists with many organisms on this earth. As a result of millions of years of evolution, the body is customized in such a way that it can live with some of them in a symbiotic relationship, and on the other hand can protect itself from the harmful ones that try to degrade its internal system. Such organisms that cause harm to human body are called pathogens and the entire defense system that works for the protection of the body against such pathogens is called immune system. This article aims in giving the detailed description about the immune system.

What is immune system?

The immune system is the host defense system consisting of various kinds of defensive cells, tissues, organs and biological processes that protect the body from the pathogens that cause various diseases. It has the ability to distinguish between the foreign cells and the own body cells and starts a cascade of processes in cases when any cell is found to be of foreign type. It is majorly of two types which has been discussed in detail in the coming paragraphs: Innate Immune System and Acquired Immune System.

Innate Immune System

  • It is the type of immune system that is present since a person’s birth.
  • It consists of layers of barriers and secretions that are pre-formed and provide the basic form of protection. This includes skin, mucosal layers in the gastro-intestinal system, acid in the stomach, tears from the lacrimal gland, macrophages to name some.
  • When a body cell encounters a foreign particle for the first time, the innate response is triggered by pattern recognition system or histocompatibility system which recognize the pathogen as not a part of the human body and then initiate a cascade of reactions for elimination of the same.
  • This system shows non-pathogen specific response and acts in a generic way for all the groups of pathogens.
  • The response shown is temporary in nature and does not give long-lasting immunity against a pathogen.

Acquired Immune System

  • It is the type of immune system that develops slowly during the growth of an individual and hence it acquires the same during its lifetime.
  • Basically it consists of antigen-antibody system where specific cells named antigens release pathogen-specific proteins called antibodies that attack them and eliminate them via numerous processes.
  • It has mainly three components: –
  • Antigen presenting cells- These are the cells that capture any foreign particle when it enters inside the body and initiate a pattern-recognition system to identify its nature.
  • T-cells– Also known as Thymus cells, these are the cells that use the recognition system to differentiate between own and foreign cells and send the destructive signals to B cells. These cells are produced by lymphoid organ named Thymus.
  • B-cells– Also known as Bursa cells, these are the killer cells that release the antibodies upon receiving signals from T-cells, to phagocytose and kill the foreign body.
  • Some of these T-cells turn into memory cells that aid in quick response in future interactions with the same pathogen and some of these B-cells get converted to plasma cells that can generate a huge number of antibodies in a short time.


Hence through this article we have made our readers aware about the basics of the immune system of the body.

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