Primary & Secondary Response
Biology: AQA A Level, topic 2.4.6
Primary Immune Response
When an individual is infected by a pathogen for the first time, a primary immune response takes place.
Slow
- The primary response is slow because it takes time for the antigens to be detected and the specific plasma cells to be activated.
- It may take several days for the pathogen to be removed by the immune system.
Symptoms
- In the primary immune response, the individual is likely to show the symptoms of the pathogen.
- The pathogen has time to cause harm to the individual before it is removed by the immune system.
Memory cells
- T cells and B cells can produce memory cells after an infection.
- Memory cells remain in the body after the infection has been removed.
- If the individual is infected again, there will be a much quicker response to the antigens.
Secondary Immune Response
When an individual is infected by a pathogen for the second time, a secondary immune response takes place.
Fast
- The secondary response is rapid because of the presence of memory cells in the body.
- The memory cells can quickly identify the antigens and produce the correct antibodies.
Stronger
- The secondary immune response is also stronger than the primary immune response.
- More plasma cells can be produced more quickly.
Symptoms
- In the secondary immune response, the individual is unlikely to show the symptoms of the pathogen.
- The pathogen is removed by the immune system before it has time to cause harm.
- The individual is said to be immune.
Test yourself on Primary & Secondary Response
Which of the following statements about the primary immune response are true?
Which of these cells do NOT produce memory cells?