12.6 Specific Immune System

Question 1

What are antigens?

Answer 1

identifying chemical

on plasma membrane of cell

which triggers immune response

Question 2

What are antibodies?

Answer 2

Y-shaped glycoproteins

made by B-cells of immune system

in response to presence of antigen

Question 3

Describe the structure of an antibody:

Answer 3

• 2 LIGHT CHAINS & 2 HEAVY CHAINS
  
  • chains held together by disulfide bridges
  • individual chains contain disulfide bridges within them
• VARIABLE REGION & CONSTANT REGION
  
  • variable: area which binds to antigen - unique to each type of antibody

Question 4

In what ways do antibodies defend the body?

Answer 4

• OPSONINS
  
  • antigen-antibody complex more easily engulfed by phagocytes
• PREVENTS PATHOGENS INVADING HOST CELLS
  
  • one part of antigen-antibody complex, pathogens cannot effectively invade host cells
• AGGLUTININS
  
  • pathogens carrying antigen-antibody complexes clump together, making it easier to phagocytose
• ANTITOXINS
  
  • bind to toxin molecules, disabling them

Question 5

Outline the process of cell-mediated immunity:

Answer 5

1. macrophage engulfs + digests pathogen, forming APC.
2. receptors on some T-helper cells are complementary to antigen. T-helper cell binds to APC & is activated.
3. Activated T-cell divides by mitosis, releasing interleukins which stimulate more T-cells to divide >> produces many T-cells with antigens complementary to bind to specific pathogen engulfed by macrophage.
4. Cloned T-cells can:
   
   1. develop into T memory cells
   2. produce interleukins which stimulate B-cells to divide
   3. develop into T-killer cells

Question 5

Outline the process of cell-mediated immunity:

Answer 5

1. macrophage engulfs + digests pathogen, forming APC.
2. receptors on some T-helper cells are complementary to antigen. T-helper cell binds to APC & is activated.
3. Activated T-cell divides by mitosis, releasing interleukins which stimulate more T-cells to divide >> produces many T-cells with antigens complementary to bind to specific pathogen engulfed by macrophage.
4. Cloned T-cells can:
   
   1. develop into T memory cells
   2. produce interleukins which stimulate B-cells to divide
   3. develop into T-killer cells

Question 6

Outline the process of humoral immunity:

Answer 6

B cell APC contains antigens from specific pathogen on its plasma membrane after phagocytosis.

1. Complementary activated T-helper cells bind to (B-cell) APC - clonal selection
2. interleukins produced by activated T-cell activate B-cells.
3. activated B-cells undergo clonal expansion, forming plasma cells + B memory cells.
4. Plasma cells produce antibodies complementary to pathogen’s antigens, memory cells divide to produce plasma cells if pathogen encountered again in secondary immune response.

Question 7

What is the function of the cell-mediated immune response?

Answer 7

responds to changes in cells

(antigens are not present in blood, e.g bacteria)

e.g viruses

Question 8

What is the function of the humoral immune response?

Answer 8

responds to antigens outside of cells