12.6 The Specifc Immune System Flashcards
What are antibodies?
- Y shaped glycoproteins called immunoglobulins which bind to specific antigens on the pathogen or toxin that triggered the immune response
When an antibody binds to an antigen it forms an antigen-antibody complex
4 ways antibodies can defend the body
1) the antibody of the antigen-antibody complex acts as an opsonin so the complex is easily engulfed and digested by phagocytes
2) most pathogens can no longer effectively invade host cells once they are part of an antigen-antibody complex
3) antibodies act as agglutinins causing pathogens carrying antigen-antibody complexes to clump together. This prevents them spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time
4) antibodies can act as anti-toxins, binding to the toxins produced by pathogens and making them harmless
Describe role and function of T lymphocytes
Lymphocytes ate involved in the specific immune response. T lymphocytes mature in the thymus gland.
- its surface is covered with receptor. The receptors bind to antigens presented by APCs
- each T lymphocyte has a different receptor on its surface.
- the receptors on the surface of the T lymphocyte binds to a complementary antigen on the surface of an APC, clonal selection takes place
- the activated T lymphocyte then undergoes clonal expansion - it dived to form clones of itself which then differentiate
Differentiated clones of T lymphocytes with different functions: - T helper cells release interleukins ( a type of cytokine) to activate B lymphocytes and T killer cells
- T killer cells destroy the pathogen carrying the antigen. They produce perforin which kills the pathogen by making holes in the cell membrane so its freely permeable
- T regulatory cells suppress the immune system (stop the immune system once the pathogen has been eliminated) this prevents autoimmune response
- T memory cells are a part of immunological memory and are part of secondary response
Describe role and function of B lymphocytes
B lymphocytes mature in the bone marrow
- they’re covered in antibodies
- when the antibody on the surface of a B lymphocyte meet a complementary antigen, it binds to it - so each B lymphocyte will bind to a different antigen
- this along with interlinking released by T helper cells activates the B lymphocyte which them divides by mitosis into plasma cells and B memory cells (this is clonal expansion)
What is cell-mediated immunity?
T lymphocytes respond to the cells of an organism that have been changed in some way e.g. by virus infection
Describe humoral immunity
In humoral immunity the body responds to antigens found outside the cells e.g. bacteria and fungi and to APCs
- a B cell with the complementary antibodies will bind to the antigens on the pathogen, the B cell engulf and processes the antigen to become an APC
1) activated T helper cells bind too the B cell APC. This is clonal selection
2) interleukins produced by the activated T helper cells activate the B cells
3) The activated B cell divides be mitosis to give clones of plasma cells and B memory cells. This is clonal expansion
4) cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to the antigens and disable them. This is the primary immune response.
5) some cloned cells develop into B memory cells. If the body is infected by the same pathogen again, the B memory cells divide rapidly to form plasma a cell clones and wipe out the pathogen very quickly before it can cause symptoms of disease. This is the secondary immune response
What is the primary response?
- pathogen enters the body for first time
- its slow as there aren’t many b lymphocutes that can make the antibody needed to bind to the pathogen
- the infected person would show symptoms of disease
What is the secondary immune response?
- if the same pathogen enters the body again, the immune response will produce as quicker, stronger immune response
- clonal selection happens faster
- memory B lymphocytes divide into plasma cells
- memory T lymphocytes kill the cell carrying the antigen
- the secondary response often gets rid of the pathogen before you begin to show symptoms
Why can’t immunity be maintained forever?
As memory B and T cells only have a limited lifespan
What are autoimmune diseases?
When the immune system can’t recognise self antigens and treats the self cells and foreign cells.
The immune system starts to attack its own healthy body tissue
3 examples of autoimmune diseases and their treatments?
Type 1 diabetes:
- it affects the insulin-secreting cells of the pancreas
Can be treated by- insulin injections, pancreas transplants, immunosuppressant drugs
Rheumatoid arthritis:
- affects joints especially in the hands, wrists and ankles and feet
- no cure, steroids and immunosuppressants and pain relief can be used
Lupus:
- affects skin and joints and causes fatigue
- can attack any organ in the body (kidney, lungs, liver, brain)
- no cure, steroids and immunosuppressants and anti-inflammatory drugs can be used for treatment
What’s a disadvantage of using immunosuppressants to treat autoimmune diseases?
Prevents the immune system working and therefore deprives the body of its natural defences against communicable diseases
