Immune System Work – Innate and Adaptive (Acquired) Immunity- Active,Passive

Immune System Work – Innate and Adaptive (Acquired) Immunity- Active, Passive -Types. The local defence systems are not effective in all cases and circumstances. Certain microbes (germs) or their poisonous secretions (toxins) do enter the deeper tissues and various organ-systems. By their special mechanisms of entry or through any breaches(an act of breaking) in the protective barriers.

How does the Immune System work?

At this stage, the blood and other body fluids start fighting against the germs or any other unacceptable foreign substance. The body fluids contain special proteins called antibodies which react with the invading germs, and antitoxins which react with their poisons (toxins) to destroy them, and thus they provide protection against disease immunity).Immune System Work - Innate and Adaptive (Acquired) Immunity- Active,Passive

What is Immune System?

Immunity is the resistance to the onset of a disease after infection by harmful germs. To define more elaborately – Immunity is the

“Capacity of our body to deal with foreign substances, e.g., bacteria, viruses, toxins, etc. that enter our body and to render them harmless.”

or simply,

“It provides resistance against disease-causing germs.”

Innate and Adaptive (Acquired) Immunity

Immunity can be classified into two main categories –

  • Innate.
  • Acquired immunity.

and their different subcategories are as follows.

Immune System: Work, Innate, Adaptive (Acquired) Immunity- Active,Passive

Innate Immunity ( Innate Immune System)

Innate immunity also called natural or native immunity. This immunity is by virtue of genetic constitutional make-up.

Innate definition

It is there in the body without any external stimulation or a previous infection.

(a) Non-specific innate immunity

A degree of natural resistance to all infections in general. For example, humans do not Suffer from the plants’ highly infectious diseases or even certain diseases of animals.

(b) Specific innate immunity

This is a natural resistance to a particular kind of germs only. Some races or some individuals do not suffer from certain infectious diseases. Example, human beings are immune to a highly infectious disease of dogs (known as Distemper), which kills about 50% of all infested dogs.

Acquired Immunity (Adaptive Immune System)

Resistance to a disease which an individual acquires during his lifetime. It may be a result of


A previous infection (actively acquired immunity), e.g., a person having once suffered from “measles” will not normally suffer from it again.


“Ready-made” antibodies supplied from outside (passively acquired immunity), e.g. a person bitten by a poisonous snake is given an anti-venin injection (venom: poison) which contains antibodies for the poison that were produced in the body of a horse.

Actively acquired immunity(Active immunity)

This is the resistance developed by an individual due to a previous infection of antigen (a chemical found on the surface of the disease-causing germ cell) which enters his body natural leading to

(i) naturally acquired active Immunity or introduced artificially, as vaccination leading to (ii) artificially acquired active immunity. In either case, the body lymphocytes react in two ways:

  • They produce antibodies which freely circulate in the blood and lymph and which binds to the microorganism to kill it.
  • They produce killer cells carrying specific receptors for foreign antigens found on invading germs.

The actively acquired immunities are usually long-lasting carried out through memory lymphocytes.

Passively acquired immunity (passive immunity)

This is the immunity provided to an individual not by his own body but from an outside source in the form of “ready-made” antibodies. The passively acquired immunity again can be of two types :

(i) Naturally acquired passive immunity. In it, the ready-made or the “pre-prepared” mother’s antibodies may reach the foetus (developing embryo) through the placenta.

(ii) Artificially acquired passive immunity. In this, the antibodies are produced in the blood of a horse or some other animal by injecting germs into its body. Antiserum injections are prepared from the serum (containing antibodies) of such animals’ blood and are injected into the body of the patient.

e.g. in the treatment of snake-bite by antivenin or that of a diphtheria patient by anti-diphtheria injections. Haffkine’s Institute in Bombay and Other institutes at Kasauli are preparing several such anti-sera. Antivenin for treat Snake-bite is also based on the same principal.

This is all about the basics of How Immune System Work – Innate and Adaptive (Acquired) Immunity- Active, Passive Types.