Immune System – Types, Components and Working

Immune System Overview

Immunity refers to the body’s ability to identify and combat harmful foreign substances such as bacteria and viruses swiftly and effectively.

Despite daily assaults from various microorganisms, the immune system acts as a protective shield, safeguarding the body.

Comprising Lymphocytes B and T, as well as Antibodies (immunoglobins produced in response to antigens), the immune system operates through the humoral immune response.

This intricate defense mechanism classifies immunity into two categories: Active and Passive. Active immunity is induced through vaccines, triggering antibody production, while Passive immunity involves the use of antisera to confer immunity against diseases.

What is the immune system, why do you need it and what are its types?

Numerous viruses and microorganisms daily attack you but have you ever thought which system is behind you for defence from these tiny illness-causing microorganisms. This is your immune system.

When your immune system is in great condition, you probably do not even see it working away to secure you all the time. However, you will know when there is something erroneous as your body immune system is your body’s built-in defence system against illness and infection. If you feel great today, thank your body immune system.

The need for healthy body immune system

A healthy and effectively operating body immune system assists you to go about daily life as you enter into contact with germs and bugs from family pets, other people, and your environment. Without a healthy body immune system, you might get infections and infectious diseases more easily, and the effects could be serious– even deadly.

Your body’s very first line of defence is its physical barriers. If viruses and germs manage to break through, there are specialised cells that will jump into action. Your bloodstream and crucial areas of your body contain leukocyte that can combat and ruin the infections and germs they find.

It is simple to take the immune system for granted since it does such an excellent task at keeping us devoid of infections. If you have got a healthy immune system, care for it and it will care for you.

Components of the Immune system

The elements of the body immune system include the lymphocytes (B and T) and the antibodies – which are unique type of proteins.

These antibodies are immunoglobulins which are synthesized by vertebrates, in action to antigens; and immobilise it, or sets in motion events that ultimately cause its damage.

Antigen or immunogen is a foreign substance, frequently a protein which stimulates the development of antibodies. Antibodies specify i.e. trigger the damage of the antigen, which stimulated their production. Antibodies are made in B-lymphocytes, then secreted into the lymph and blood where they flow freely.

Working of Immune system

T-cells acknowledge antigen, then battle micro-organisms and/ or effect the rejection of foreign tissues (in case of tissue transplant). This is called cell-mediated reaction. B-cells acknowledge antigen and form plasma cell clone. These plasma cells synthesise and release antibodies into the blood plasma and tissue fluid. Here antibodies attach to the surfaces of germs and accelerate their phagocytosis, or combine with and neutralise toxins produced by bacteria, by producing antitoxins.

This is called humoral Immune response. When we get the vaccination, versus a specific disease (antigen), we end up being immune to that infection or disease. If we get a vaccination against polio, smallpox, measles, mumps, and so on, once in our lifetime, we are protected or ended up being unsusceptible to that infection in our future life.

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Types of Immunity
Active Immunity

The use of vaccines, which stimulate the production of antibodies in the body, and making a person immune against the disease or infection, is called active immunity. But this active immunity has been achieved by artificially introducing, antigens in the body, so it is called artificially caused active immunity.

But, when an individual is exposed to infection (antigen) – ends up being ill, and for the most part endures then this immunity, established versus that illness is called naturally induced immunity or autoimmune reaction.

Passive Immunity

In contrast to active immunity, in which case antigens are presented to stimulate the production of antibodies, by artificial or natural technique; antibodies are injected in the form of antisera, to make a person immune against disease, this is called passive immunity. In the body, antigen-antibody complexes are formed which are used up by phagocytes and destroyed. The patient is spared the issues (or possibly death) triggered by the infection or venom.

Passive immunity response is instant, but not long-lasting. Because no time at all is taken for the production of sufficient level of antibodies, (as antibodies are being injected) and after the level of antibodies is decreased or they are used up – No more antibodies production exists.

The method of passive immunization is used to fight active infections of, tetanus, contagious hepatitis, rabies, snake bite venom, etc. When it comes to snake bite venom passive immunity is produced by the antitoxins so the serum is called antivenom serum.

Frequently Asked Questions (FAQs) – Immune System

  1. What is the immune system, and why is it essential for the body?
    • The immune system is the body’s built-in defense mechanism against diseases and infections caused by foreign substances like bacteria and viruses. It recognizes and fights these invaders to maintain overall health.
  2. How does the immune system provide defense against daily threats?
    • The immune system operates continuously, defending the body against viruses and microorganisms. It has physical barriers and specialized cells, such as white blood cells, to combat and eliminate threats.
  3. Why is a healthy immune system important for daily life?
    • A healthy and efficient immune system ensures that the body can resist infections and diseases encountered in daily life. Without it, susceptibility to infections increases, leading to potentially severe consequences.
  4. What are the components of the immune system?
    • The immune system consists of lymphocytes (B and T cells) and antibodies, which are proteins synthesized by the body in response to antigens. These components work together to eliminate foreign substances.
  5. How does the immune system work against infections?
    • The immune system employs a humoral immune response. T-cells recognize and combat microorganisms, while B-cells form plasma cells that release antibodies. These antibodies neutralize toxins and accelerate the phagocytosis of bacteria.
  6. What is the role of antibodies in the immune system?
    • Antibodies, also known as immunoglobulins, are proteins produced in response to antigens. They attach to the surfaces of bacteria, neutralize toxins, and contribute to the destruction of antigens, providing immunity.
  7. What is immunity, and what are its types?
    • Immunity is the body’s ability to recognize and eliminate foreign substances. There are two types of immunity: active immunity, achieved through vaccines, and passive immunity, obtained by injecting antibodies.
  8. Explain active immunity and how it is achieved.
    • Active immunity is achieved by stimulating the production of antibodies through vaccines. Vaccines introduce antigens into the body, triggering an immune response and making the person immune to the disease.
  9. What is passive immunity, and when is it used?
    • Passive immunity involves injecting antibodies, often in the form of antisera, to make a person immediately immune to a disease. It is used in emergencies to provide rapid protection but is not long-lasting.
  10. How does the immune system respond to infections naturally?
    • When an individual is exposed to an infection and recovers, the immunity developed against that disease is called naturally induced immunity or autoimmune reaction.
  11. What is the difference between active and passive immunity?
    • Active immunity is induced by introducing antigens through vaccines, while passive immunity involves injecting antibodies directly into the body. Active immunity is long-lasting, while passive immunity is immediate but temporary.
  12. When is passive immunization used, and for what diseases?
    • Passive immunization is used to fight active infections, such as tetanus, contagious hepatitis, rabies, and snakebite venom. It provides immediate protection but is not a long-term solution.
  13. How is passive immunity used in the case of snakebite venom?
    • Passive immunity against snakebite venom is produced by injecting antitoxins, resulting in the production of antivenom serum, providing rapid protection against the venom.
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Summarizing Immune System

The immune system is a complex defense mechanism within the body, providing protection against harmful foreign substances like bacteria and viruses. Comprising lymphocytes B and T, as well as antibodies (immunoglobulins), the immune system operates through humoral immune responses, demonstrating two key types of immunity: Active and Passive.

1. The Need for a Healthy Immune System:

  • The immune system acts as the body’s innate defense against daily attacks from viruses and microorganisms. A well-functioning immune system operates silently, defending against illnesses. When in good condition, it is instrumental in maintaining overall health and preventing infections.

2. Components of the Immune System:

  • The immune system’s components include lymphocytes (B and T cells) and antibodies. These immunoglobulins, synthesized in response to antigens, play a crucial role in neutralizing or damaging foreign substances. Antigens, typically proteins, stimulate the production of antibodies, primarily formed in B-lymphocytes.

3. Working of the Immune System:

  • T-cells recognize antigens and engage in cell-mediated reactions, combating microorganisms and rejecting foreign tissues. B-cells recognize antigens, form plasma cell clones, and release antibodies into the bloodstream. These antibodies attach to bacteria surfaces, enhancing phagocytosis or neutralizing toxins, contributing to the humoral immune response.

4. Types of Immunity:

  • Active Immunity: Achieved through vaccines, actively introducing antigens into the body to stimulate antibody production, providing long-lasting protection against diseases.
  • Passive Immunity: Involves injecting antibodies, known as antisera, to provide immediate but temporary protection. Antigen-antibody complexes are formed and subsequently destroyed by phagocytes.

5. Passive Immunization and Its Use:

  • Passive immunization is employed to combat active infections, such as tetanus, contagious hepatitis, rabies, and snakebite venom. The antitoxins present in antisera, especially in the case of snakebite venom, contribute to immediate protection against the respective toxins.

In essence, understanding the immune system’s intricacies and the types of immunity emphasizes the significance of maintaining a healthy immune system for overall well-being and disease prevention. The collaboration between lymphocytes, antibodies, and other components showcases the remarkable defense mechanisms that shield the body from potential threats.

Quiz about Immune System

1. What is immunity?

  • a. The capacity of a body to create viruses
  • b. The ability of a body to recognize and fight foreign substances
  • c. The production of antibodies only
  • d. The destruction of leukocytes

2. What are the components of the immune system?

  • a. Red blood cells
  • b. Lymphocytes B and T, and Antibodies
  • c. Platelets
  • d. Muscles and bones

3. What is the humoral immune response?

  • a. Physical barriers against infections
  • b. The working of the immune system
  • c. Production of antibodies
  • d. Passive immunity

4. How many types of immunity are there?

  • a. Three
  • b. Two
  • c. Four
  • d. Five

5. How is active immunity achieved?

  • a. Through physical exercise
  • b. By using antibiotics
  • c. Through vaccines
  • d. By avoiding contact with germs
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6. What is the body’s first line of defense against infections?

  • a. Antibodies
  • b. Physical barriers
  • c. T-cells
  • d. Antigens

7. What is the primary function of antibodies?

  • a. Recognize antigens
  • b. Destroy leukocytes
  • c. Stimulate the immune system
  • d. Produce antigens

8. What is the role of T-cells in the immune system?

  • a. Recognize antigens and produce antibodies
  • b. Destroy antigens directly
  • c. Form plasma cell clones
  • d. Attack foreign tissues

9. Which type of immunity involves the use of vaccines?

  • a. Natural immunity
  • b. Passive immunity
  • c. Artificially caused active immunity
  • d. Autoimmune reaction

10. What is the immediate response of passive immunity?

  • a. Long-lasting antibody production
  • b. Delayed production of antibodies
  • c. Instant, but not long-lasting
  • d. Production of antigens

11. Why is a healthy immune system essential for daily life?

  • a. To combat diseases through daily immune attacks
  • b. To create viruses
  • c. To stimulate antibody production
  • d. To destroy leukocytes

12. What is the function of phagocytes in the immune system?

  • a. Produce antibodies
  • b. Recognize antigens
  • c. Attack and destroy foreign particles
  • d. Form plasma cell clones

13. What is the purpose of passive immunization?

  • a. To create antibodies
  • b. To stimulate the immune system
  • c. To fight active infections
  • d. To destroy antigens

14. What is the primary role of B-cells in the immune system?

  • a. Attack and destroy foreign tissues
  • b. Form plasma cell clones
  • c. Recognize antigens and produce antibodies
  • d. Destroy leukocytes

15. How is passive immunity achieved in the case of snake bite venom?

  • a. Through vaccines
  • b. By injecting antibodies (antivenom serum)
  • c. Naturally induced immunity
  • d. Through physical barriers


  1. b, 2. b, 3. c, 4. b, 5. c, 6. b, 7. a, 8. d, 9. c, 10. c, 11. a, 12. c, 13. c, 14. c, 15. b