Primary and secondary responses:

Question 1

Primary immune response

Answer 1

Primary immune response: The initial response caused by a first infection, initiated by detection of foreign antigens on pathogen.
Slow – there aren’t many B cells that can make right antibody.
- Clonal selection is slow as pathogen/APC has to come into contact with specific B and T lymphocytes.
- Once B cells activated these need to produce enough identical plasma cells (clonal expansion) to
produce enough antibody to overcome infection – takes a few days. - While this is happening person will show symptoms.
Once pathogen has been eliminated B & T lymphocytes produce memory cells that remain in blood for a long time, they provide long-term immunological memory, person can respond quickly to 2nd infection.

Question 2

Secondary immune response

Answer 2

Secondary immune response: A quicker and stronger response caused by a second or subsequent infection by the same pathogen (caused by activation of memory cells, not B/T cells like primary).
Clonal selection happens faster, as there are many memory cells.
B memory lymphocytes are activated and divide into plasma cells that
all produce specific antibody – correct antibody is produced faster.
- Amount of antibody rises faster and reaches higher maximum.
T memory lymphocytes are activated sooner and divide in right type of T killer cell to kill pathogen.
- Secondary response usually eliminates pathogen before symptoms are experienced (no symptoms).

Question 3

Autoimmune diseases:

Answer 3

Diseases that occur when immune system attacks part of the body. Arises when antibodies attack our own antigens (detect own cells as foreign) prevented by T regulatory cells. Caused by genetic and environment.
• Arthritis – painful inflammation of a joint, when antibodies attack membranes around the joint.
• Lupus – caused by antibodies attacking certain proteins in cells in connective tissues, causing
inflammation and pain. Can affect skin and joints, as well as organs.