immune

Question 1

Name and describe two lymphatic structures in which immunity to a foreign agent is likely to occur (2 marks)

Answer 1

1) lymphoid nodules are aggregations of unencapsulated lymphocytes and macrophages in mucosa and submucosa
2) lymph nodes are encapsulated aggregations of lymphocytes and macrophages located along lymph vessels in many parts of the body

Question 2

Explain what innate defense mechanisms are and list six of its components (3 marks).

Answer 2

mechanisms that defend against a foreign agent even thought the body has not previously encountered that agent

• barriers like skin and mucous membranes
• secretions like tears, saliva, sweat
• phagocytic cells
• inflammation
• complement
• interferon

Question 3

Describe complement and its role in defense (2 marks).

Answer 3

• a group of proteins that circulate in the blood and are activated when antigen bonds to antibody
• forms a membrane attack complex that inserts in the cell membrane and results in lysis of cell

Question 4

Describe the role of interferons in defense.

Answer 4

• proteins that are produced by a cell that is infected by virus
• prevent the replication of viruses in a cell and the infection of cell by virus

Question 5

List the two main components of immunity and briefly explain how they differ.

Answer 5

1) humoral immunity results from the action of antibodies

2) cell mediated immunity results from the action of T lymphocytes

Question 6

List the four most important structures involved in immunity (2 marks)

Answer 6

1) antigens
2) antibodies
3) antigen presenting cells
4) lymphocytes

Question 7

Explain what antigens are.

Answer 7

-complex, large molecules that are recognized by antibodies or T cell receptors and trigger an immune response

Question 8

Explain how T cells and B cells differ in their development.

Answer 8

• T cells migrate from the bone marrow to the thymus gland where they become T cells
• B cells remain in the bone marrow

Question 9

Explain the role of cytotoxic T cells in the immune system (2 marks

Answer 9

-have receptors on their surface that bind to antigen and trigger the release of cytotoxic molecules that kill surrounding cells (cell mediated immunity)

Question 10

Explain the role of B cells in the immune system (2 marks).

Answer 10

secrete antibodies that bind to antigen and inactivate them or trigger other defense reactions (humoral immunity)

Question 11

Explain the role of helper T cells in the immune system

Answer 11

-have receptors that bind to antigen, triggering the release of cytokines that activate cytotoxic T cells and B cells

Question 12

Explain the role of macrophages in the immune system

Answer 12

• engulf foreign agents, break them down into smaller fragments and display these fragments on the surface of the cell
• antigens must be “presented” by macrophages in order to be recognized by T helper or cytotoxic T cells

Question 13

Explain what antibodies (immunoglobulins) are.

Answer 13

• proteins that are shaped like a two-pronged fork (each prong can bond to an antigen)
• soluble and are transported in body fluids, especially blood and interstitial fluid

Question 14

Name the five major classes and describe the role of each (3 marks)

Answer 14

IgG is common in blood and a major component of humoral immunity

• IgM is present in blood and a part of humoral immunity
• IgA is present in body secretions, especially the digestive tract
• IgE is present on the surface of basophils and triggers allergic response when it binds to antigen (allergen)
• IgD is located on the B lymphocyte and is involved in lymphocyte activation

Question 15

List 5 processes that can be triggered by binding of antibody to antigen (3

Answer 15

1) inactivation of antigen
2) precipitation of antigen (easier for phagocytosis)
3) agglutination (cell clumping) of cell surface antigens
4) activation of complement
5) release of histamine from basophils

Question 16

Distinguish between a primary and secondary immune response

Answer 16

• primary response occurs first time an antigen is contacted and results in a slow (several weeks) and small humoral and cell mediated response
• secondary response occurs after an antigen has already been contacted and results in a more rapid and more intense humoral and cell mediated response (often sufficient to prevent the infectious agent from causing symptoms)

Question 17

Explain what happens if a person with blood type ____ is transfused with type ____
blood (replace the blanks with any of types A, AB, B, O, Rh+ve or Rh-ve).

Answer 17

1) type A individual will accept blood from blood types A and O; anti-B antibodies of type A individual will react with type B and type AB blood
2) type AB individual will accept blood from blood types A, B, AB and O; they do not have anti-A or anti-B antibodies
3) type B individual will accept blood from blood types B and O; anti-A antibodies of type B individual will react with type A and type AB blood
4) type O individual will accept blood ONLY from blood types O; anti-A and anti-B antibodies of type O individual will react with type A and type B and type AB blood
5) Rh+ve individual can accept blood from either Rh+ve or Rh-ve donor
6) Rh-ve individual can accept blood from either T=Rh+ve or Rh-ve donor…BUT should not receive Rh+ve blood because they will develop immunity to it and react to a second transfusion with Rh+ve blood

Question 18

Explain what hemolytic disease of the newborn is and explain how it could develop.

Answer 18

• occurs if a women who is Rh-ve carries an Rh+ve child (father is Rh+ve) AND the babies blood enters the mother’s blood
• mother develops immune response to Rh+ve blood that may not develop quickly enough to interfere with pregnancy but will put subsequent pregnancies at risk
• ant-Rh antibodies are transferred from the mother’s blood across the placenta into the fetus’ blood and causes hemolysis
• baby develops anemia and may not be able to replace red cells fast enough to compensate for destruction by mothers antibodies.

Question 19

Explain what Rhogam is and how it is used as a therapeutic agent.

Answer 19

• anti-Rh antibodies that are administered to Rh-ve women early in pregnancy
• Rhogam binds to any fetal cell that enter the mother’s circulation and destroy them before they cause immunity to develop in the mother