Immunology

Question 1

Describe the non-specific defence mechanisms the body may launch against pathogens. 5marks

Answer 1

-pathogen is engulfed by phagocyte
-pathogen held in a phagosome
-lysosomes fuse with the phagosome releasing hydrolytic digestive enzymes
- these digest the pathogen
-antigens of pathogen are presented of surface of the phagosome (antigen presenting cell)
-waste removed by exocytosis

Question 2

Describe how a pathogen destroys a pathogen present in the blood. 3marks

Answer 2

-pathogen is engulfed by phagosome and held in a phagosome
-lysosomes fuse with phagosome releasing hydrolytic digestive enzymes
-which digest pathogen

Question 3

Give two types of cell other than pathogens that can stimulate an immune response.

Answer 3

Cancer cells
Cells infected with a virus

Question 4

When a vaccine is given to a person, it leads to the production of antibodies against the disease causing organism. Describe how.

Answer 4

-vaccine contains antigen of pathogen
-phagocytosis occurs leading to the pathogens antigens being presented on the cell membrane of phagocyte
-specific T helper cell with complementary receptor protein binds to antigen
- T helper cell then binds to specific complementary antibody on B cell stimulating it to divide rapidly by mitosis into memory cells and plasma cells
-plasma cells produces large amounts specific antibody

Question 5

Explain how the humoral response leads to immunity. 3 marks

Answer 5

• B cell with specific antibody to antigen rapidly divides by mitosis
• into plasma and memory cells
  -on secondary infection antibodies are produced at a faster rate in larger amounts

Question 6

Describe and role of antibodies in stimulating phagocytosis. 2 marks

Answer 6

-antibodies bind to pathogen
-acting as a marker attracting phagocyte

Question 7

Describe the difference between passive and active immunity. 6 marks

Answer 7

-active immunity involves memory cells whereas passive immunity does not
- active immunity involves production of antibodies by plasma cells whereas passive immunity the antibodies are give from outside
-active immunity is long term as the body produces antibodies in response to the antigen whereas passive immunity is short term as antibodies given is broken down
-active immunity takes a longer time to have an effect whereas passive immunity is fast acting

Question 8

State why some antibodies are referred to as monoclonal.

Answer 8

They are produced from the same plasma cell

Question 9

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to suggest why. 3 marks

Answer 9

• antibodies have a specific primary structure
• so have a specific tertiary structure
  -only bind to one complementary antigen

Question 10

Describe the structure of HIV. 5 marks

Answer 10

• RNA as genetic material
• reverse transcriptase
• capsid
• phospholipid envelope
• attachment proteins

Question 11

Describe how a person with HIV will develop AIDS and die of secondary infections. 4 marks

Answer 11

• high viral load caused increased destruction of T helper cells
• so less stimulation of B cell with specific antibody
• less production of antibodies
• less able to destroy other pathogen

Question 12

Describe the role of antibodies in producing a positive ELISA test. 4 marks

Answer 12

• antibody binds to complementary antigen
• second antibody with enzyme is added
• antibody attached to antigen
• substrate is added causing colour change

Question 13

Describe how HIV replicates in t helper cell 4m

Answer 13

RNA is converted to DNA using reverse transcriptase
DNA is inserted into T helper cell DNA
DNA transcribed into hiv mRNA
Which is translated into new hiv proteins