9.4 Types of Acquired Immunity

There are two ways to acquire adaptive immunity: active immunity and passive immunity. Both types may be acquired naturally or artificially. Providing immunity artificially is called immunization.

Definition

Active Immunity: Active immunity is the kind of immunity which is obtained as a result of an infection. The body manufactures its own antibodies when exposed to an infectious agent.

Passive Immunity: In passive immunity antibodies from one individual are passed into another individual.

Immunization: Providing immunity artificially is called immunization.

Main Idea

• There are two ways to acquire adaptive immunity:
• Both types may be acquired naturally or artificially.
• Providing immunity artificially is called immunization.
• Active immunity can be natural or artificial.
• Passive immunity can be natural or artificial.

Core Concept

• Active immunity = body manufactures its own antibodies
• Passive immunity = antibodies passed from one individual to another
• Natural active immunity = obtained as a result of an infection
• Artificial active immunity = achieved by vaccination
• Natural passive immunity = antibodies from mother to foetus/infant
• Artificial passive immunity = antibodies formed in one individual injected into another

Detailed Explanation

Types of Acquired Immunity

There are two ways to acquire adaptive immunity: (a) Active Immunity (b) Passive Immunity. Both types may be acquired naturally or artificially. Providing immunity artificially is called immunization.

Natural Active Immunity

• Natural active immunity is the kind of immunity, which is obtained as a result of an infection.
• The body manufactures its own antibodies when exposed to an infectious agent.
• This type of immunity is most effective and generally persists for a long time, sometimes even for life.
• For example, you can get measles only once in your life, as it gives lifelong natural active immunity.

Artificial Active Immunity

• Artificial Active Immunity (vaccination) is achieved by injecting (or administering orally) small amounts of antigen, called the vaccine, into the body of an individual.
• The process is called vaccination.
• The antigen stimulates the body to manufacture antibodies against other antigen.
• Often a second, booster is given and this stimulates a much quicker production of antibody which is long lasting and which protects the individual from the disease for a considerable time.
• Several types of vaccine are currently in use.

Passive Immunity

• In passive immunity antibodies from one individual are passed into another individual.
• They give immediate protection, unlike active immunity, which takes a few days or weeks to build up.
• However, it only provides protection against infection for a few weeks, for the antibodies are broken down by the body's natural processes, so their number slowly fall and protection is lost.

Natural Passive Immunity

• It may be gained naturally.
• For example, antibodies from a mother can cross the placenta and enter her foetus.
• In this way they provide protection for the baby until its own immune system is fully functional.
• Passive immunity may also be provided by colostrum, the first secretion of the mammary glands.
• The baby absorbs the antibodies through its gut.

Artificial Passive Immunity

• Antibodies which have been formed in one individual are extracted and then injected into the blood of another individual which may or may not be of the same species.
• They can be used for immediate protection if a person has been; or is likely to be, exposed to a particular disease.
• For example, specific antibodies used for combating tetanus and diphtheria used to be cultured in horses and injected into humans.
• Only antibodies of human origin are now used for humans.
• Antibodies against rabies and some snake venoms are also available.
• Antibodies against the human rhesus blood group antigen are used.

Do You Know?

The first antibody-based therapies were used to treat snake bites and were called antivenoms!

Summary Table of Types of Acquired Immunity

Intermediate Level

Types of Acquired Immunity

Comparison of Active and Passive Immunity

Summary of Active Immunity

Summary of Passive Immunity

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Two ways to acquire adaptive immunity: active and passive.
• 2. Both types may be acquired naturally or artificially.
• 3. Providing immunity artificially is called immunization.
• 4. Natural active immunity is obtained as a result of an infection.
• 5. Artificial active immunity is achieved by vaccination.
• 6. Natural passive immunity is from mother to foetus/infant.
• 7. Artificial passive immunity is antibodies injected into another.
• 8. Active immunity is most effective.
• 9. Active immunity persists for a long time.
• 10. Passive immunity gives immediate protection.
• 11. Passive immunity lasts only a few weeks.
• 12. Antibodies in passive immunity are broken down over time.
• 13. Colostrum provides passive immunity.
• 14. Antivenoms are an example of artificial passive immunity.
• 15. Tetanus antibodies are an example of artificial passive immunity.
• 16. Antibodies against rabies are available.
• 17. Antibodies against rhesus blood group antigen are used.
• 18. First antibody-based therapies were antivenoms.
• 19. Vaccination stimulates antibody production.
• 20. Booster doses stimulate quicker production of antibody.

Remember

• - Active immunity = body manufactures its own antibodies
• - Passive immunity = antibodies passed from one individual to another
• - Natural active immunity = obtained as a result of an infection
• - Artificial active immunity = achieved by vaccination
• - Natural passive immunity = antibodies from mother to foetus/infant
• - Artificial passive immunity = antibodies formed in one individual injected into another
• - Immunization = providing immunity artificially

Common Mistakes

• 1. Confusing active and passive immunity — Active = body makes antibodies; passive = antibodies passed.
• 2. Mixing up natural and artificial — Natural = infection or mother; artificial = vaccination or injection.
• 3. Forgetting the duration — Active = long-lasting; passive = short-lasting.
• 4. Forgetting the onset — Active = days or weeks; passive = immediate.
• 5. Mixing up the examples — Measles = natural active; vaccines = artificial active; colostrum = natural passive; antivenoms = artificial passive.
• 6. Thinking passive immunity provides memory — Passive immunity does not provide memory.
• 7. Believing active immunity is immediate — Active immunity takes days or weeks.
• 8. Mixing up the sources — Natural active = infection; artificial active = vaccination.
• 9. Forgetting the role of colostrum — Provides passive immunity.
• 10. Thinking antivenoms are active immunity — Antivenoms are passive immunity.

Quick Revision

There are two ways to acquire adaptive immunity: (a) Active Immunity (b) Passive Immunity. Both types may be acquired naturally or artificially. Providing immunity artificially is called immunization. Natural active immunity is the kind of immunity, which is obtained as a result of an infection. The body manufactures its own antibodies when exposed to an infectious agent. This type of immunity is most effective and generally persists for a long time, sometimes even for life. For example, you can get measles only once in your life, as it gives lifelong natural active immunity. Artificial Active Immunity (vaccination) is achieved by injecting (or administering orally) small amounts of antigen, called the vaccine, into the body of an individual. The process is called vaccination. The antigen stimulates the body to manufacture antibodies against other antigen. Often a second, booster is given and this stimulates a much quicker production of antibody which is long lasting and which protects the individual from the disease for a considerable time. Several types of vaccine are currently in use. In passive immunity antibodies from one individual are passed into another individual. They give immediate protection, unlike active immunity, which takes a few days or weeks to build up. However, it only provides protection against infection for a few weeks, for the antibodies are broken down by the body's natural processes, so their number slowly fall and protection is lost. It may be gained naturally. For example, antibodies from a mother can cross the placenta and enter her foetus. In this way they provide protection for the baby until its own immune system is fully functional. Passive immunity may also be provided by colostrum, the first secretion of the mammary glands. The baby absorbs the antibodies through its gut. Antibodies which have been formed in one individual are extracted and then injected into the blood of another individual which may or may not be of the same species. They can be used for immediate protection if a person has been; or is likely to be, exposed to a particular disease. For example, specific antibodies used for combating tetanus and diphtheria used to be cultured in horses and injected into humans. Only antibodies of human origin are now used for humans. Antibodies against rabies and some snake venoms are also available. Antibodies against the human rhesus blood group antigen are used.

60-Second Revision

• Active immunity = body manufactures its own antibodies
• Passive immunity = antibodies passed from one individual to another
• Natural active immunity = obtained as a result of an infection
• Artificial active immunity = achieved by vaccination
• Natural passive immunity = antibodies from mother to foetus/infant
• Artificial passive immunity = antibodies formed in one individual injected into another
• Immunization = providing immunity artificially
• Warning: Active immunity is long-lasting; passive immunity is short-lasting

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• Chapter:
• 9. Immunity

• Topic:
• 9.3.5 DISORDERS OF IMMUNE SYSTEM

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