Topic 6B - Developing Immunity

Front 1

What occurs when a pathogen enters the body for the first time?

Back 1

1. The antigens on its surface activate the immune system. The non-specific immune response is activated, activating the specific response (primary response). It is slow; there aren't many B cells that can make the antibody needed to bind to the antigen.
   
2. Eventually, enough antibodies are produced to overcome the infection.
   

Front 2

What happens after being exposed to an antigen?

Back 2

• Memory cells are produced by T and B cells, which remain in the body for a long time. It remembers the specific antigen and records the specific antibody needed to bind to it.
  
• The person is now immune - the immune system will respond quickly to a second infection and will produce a strong, quick secondary response.
  

Front 3

What is the difference between T and B memory cells?

Back 3

T memory cells divide into the T cell to kill the antigen. B memory cells divide into plasma cells that produce the antibody to the antigen. The secondary response deals with the infection before symptoms show.

Front 4

What is active immunity?

Back 4

The type of immunity when your immune system makes its own antibodies after being stimulated by the antigen.

Natural - become immune after disease

Artificial - become immune after a vaccine.

Front 5

What is passive immunity?

Back 5

The type of immunity from being given antibodies made by a different organism - you don't produce antibodies of your own.

Natural - a baby becomes immune after receiving antibodies from the mother through the placenta.

Artificial - being injected with antibodies.

Front 6

What are vaccines?

Back 6

1. Vaccines help avoid suffering from the disease while your specific immune response occurs.
   
2. They contain antigens that stimulate the primary immune response against a pathogen, without causing disease. Memory cells are made so you become immune without symptoms.
   
3. Some vaccines have different antigens to protect against different strains of pathogen, which are created by antigenic variation.
   

Front 7

What is the evolutionary race?

Back 7

1. Over millions of years vertebrates have evolved better immune systems to fight a greater variety of pathogens.
   
2. Pathogens also evolve to evade the immune systems.
   
3. The struggle is known as the evolutionary race (they constantly try to overcome each other).
   

Front 8

What are HIV's evasive mechanisms?

Back 8

It kills the cell it infects, reducing immune system cells, reducing risk of detection. It has high genetic mutation rate for antigen proteins, forming new strains of the virus (antigenic variation). Memory cells produced for one strain won't recognise other strains so a primary response is needed for each strain. It disrupts antigen presentation in infected cells, preventing recognition by the immune system

Front 9

What are Mycobacterium tuberculosis' evasion mechanisms?

Back 9

1. When they infect lungs, they are engulfed by phagocytes. They produce substances that prevent the lysosome from fusing with the phagocytic vacuole, meaning the bacteria aren't broken down and they can replicate undetected.
   
2. It also disrupts antigen-presentation, preventing detection of infection.