2: CELLS - SPECIFIC IMMUNE RESPONSE

Question 1

What is a T-cell/T-lymphocyte and what do they do?

Answer 1

• type of white blood cell
• have receptor proteins that allow them to bind to complementary antigens presented by phagocytes
• helper T-cells (Th cells) release chemical signals that activate and stimulate phagocytes and B-cells
• cytotoxic T-cells (Tc cells) kill abnormal and foreign cells

Question 2

What is a B-cell/B-lymphocyte and what do they do?

Answer 2

• type of white blood cell
• produce specific antibodies which bind to complementary antigens to form an antigen-antibody complex

Question 3

Where are lymphocytes produced?

Answer 3

bone marrow

Question 4

What is the cellular response?

Answer 4

T-cells and other immune system cells they interact with (eg: phagocytes)

Question 5

Describe the process of cellular response?

Answer 5

• macrophage engulfs and digests pathogen using lysozymes and the antigen is presented on the surface of the macrophage
• clonal selection - T-cells with receptors complementary to the antigen on the antigen presenting cell bind and the correct T-cells are selected and activated
• clonal expansion - activated T-cells multiply rapidly by mitosis
• Th cells release chemicals (cytokines and interleukins) to activate B-cells and phagocytes
• Tc cells release molecules to kill pathogen/abnormal/infected/foreign cell (apoptosis)

Question 6

What is the humoral response?

Answer 6

B-cells, clonal selection and production of monoclonal antibodies

Question 7

Describe the process of humoral response

Answer 7

• clonal selection - antigens on surface of B-cell (complementary to antigen) bind to antigen on pathogen
• clonal expansion - activated B-cells divide by mitosis to form plasma cells (clones of B-cells)
• plasma cells secrete lots of a specific antibody (monoclonal antibodies)

Question 8

What are memory cells?

Answer 8

• some B-cells and T-cells differentiate into memory cells
• memory cells can remember a specific antigen so immune response is rapid the next time the body is exposed to that antigen

Question 9

What is the structure of an antibody?

Answer 9

• 4 polypeptide chains held together by disulfide bridges
• 2 longer chains (heavy chains)
• 2 shorter chains (light chains)
• antibodies have variable regions which have a specific tertiary structure making them complementary to a specific antigen
• all antibodies have the same constant regions

Question 10

Explain 2 ways in which antibodies are involved in immune response?

Answer 10

• neutralisation - formation of antigen-antibody complex prevents pathogen from binding to host cell
• agglutination - antibodies have 2 variable regions so they can bind to 2 antigens at once causing pathogens to clump together. phagocytes can then bind to the constant region of an antibody and phagocytose many pathogens at once