11-9 Active Immunity (Cambridge AS A Level Biology, 9700)

Summary

This video explains immunity in the context of infectious diseases, focusing on how the body fights off pathogens. It distinguishes between active and passive immunity. Active immunity involves the body's immune response to infection, including the production of memory cells that offer long-term protection. Passive immunity, on the other hand, doesn't require the body to work directly, as immunity is transferred from another source. The video also discusses natural and artificial active immunity, with vaccines being a prime example of artificial active immunity. It concludes that memory cells provide lasting immunity, preventing future infections.

Takeaways

• 😀 Immunity is the ability to fight off or resist infections caused by pathogens, such as viruses or bacteria.
• 😀 Immunity can be obtained through two types: active immunity and passive immunity.
• 😀 Active immunity requires the body’s immune system to work and produce its own defenses, like antibodies.
• 😀 Passive immunity involves receiving ready-made antibodies or other immune factors without the body’s direct involvement.
• 😀 Active immunity can happen naturally when a pathogen infects the body, triggering an immune response.
• 😀 In active immunity, memory B lymphocytes are produced, enabling the body to respond more quickly if the same pathogen invades again.
• 😀 Vaccination is a form of artificial active immunity, where weakened or dead pathogens (or just their antigens) are introduced to stimulate an immune response.
• 😀 A vaccine does not make the body sick but prompts the immune system to produce memory B cells for long-term protection.
• 😀 Natural infections, such as with diseases like polio or measles, can leave permanent damage even if the person recovers.
• 😀 The benefit of vaccination is that it helps build immunity without the risk of suffering permanent damage from the disease.

Q & A

What is immunity in the context of infectious diseases?

Immunity refers to the ability of the body to fight off infections caused by pathogens. This can either mean resisting an infection entirely or fighting off the infection after it occurs, eventually leading to recovery.

What are the two main types of immunity discussed in the video?

The two main types of immunity discussed are active immunity and passive immunity. Active immunity requires the body to work in response to an infection, while passive immunity involves external assistance without the body's direct involvement.

How does active immunity work?

Active immunity occurs when the body produces its own immune response to a pathogen. This process includes the activation of B lymphocytes, clonal selection, and the production of antibodies that help fight off the infection.

What is the difference between natural and artificial active immunity?

Natural active immunity happens when the body is naturally exposed to a pathogen, gets sick, and then recovers. Artificial active immunity occurs when a vaccine, containing dead or weakened pathogens, is introduced into the body to stimulate the immune response without causing illness.

Why does the body respond more quickly to infections after the first encounter with a pathogen?

After the first encounter with a pathogen, the body creates memory B lymphocytes. These memory cells allow the immune system to respond faster and more effectively if the same pathogen infects the body again in the future.

What is the role of memory B lymphocytes in immunity?

Memory B lymphocytes are responsible for remembering a previous pathogen encounter and enabling a faster and stronger immune response if the pathogen infects the body again. They help provide long-term protection.

What is the significance of vaccines in artificial active immunity?

Vaccines play a crucial role in artificial active immunity by introducing dead or weakened pathogens, or just their antigens, into the body. This stimulates the immune system to produce antibodies and memory cells without causing illness, providing protection against future infections.

What is clonal selection, and how does it relate to immune responses?

Clonal selection is the process by which specific B lymphocytes are activated by recognizing a foreign antigen. This leads to the production of plasma cells, which release antibodies, and memory B cells, which offer long-term immunity.

Can passive immunity be acquired without the body’s immune system doing any work?

Yes, passive immunity involves receiving immunity from an external source, such as antibodies from another individual or from vaccines that contain pre-formed antibodies, without the body's immune system having to actively produce them.

Why might natural active immunity not always be sufficient?

Natural active immunity might not always be sufficient because some infections can cause permanent damage or death before the body has time to mount an effective immune response. For example, diseases like polio or measles can result in long-term damage, even if the person recovers from the initial infection.