Chapter 17 Immunologic Disorders

Question 1

Hypersensitivity - Allergic Response

Answer 1

• An antigenic response beyond that considered normal

- Immune response to an allergen - An antigen that causes hypersensitivity

Question 2

Type 1 Hypersensitivity

Answer 2

Anaphylactic Response
Have:
1) First encounter
2) Second encounter

Question 3

Anaphylactic First Encounter

Answer 3

First encounter with allergen causes B cells to differentiate into plasma and memory cells

• Plasma cells make IgE - binds to mast cells or basophils
• No apparent symptoms

Question 4

Anaphylactic Second Encounter

Answer 4

• IgE molecules bind to the antigen
• Mast cell or basophil degranulates - releasing histamine
• Histamine triggers inflammation:
  1) Vasodilation, swelling, redness, itchiness
  2) Mucous production - tears, runny nose
  3) Difficulty breathing
• If the allergen is spread throughout the body:
  Sudden decreases in blood pressure – Anaphylactic Shock (ex. Food allergies)

Question 5

Antihistamine (Treatment for Hypersensitivity)

Answer 5

• Blocks the action of histamine
• Histamine still produced but cannot trigger inflammation
• Works well for mild symptoms (Ex. Hay Fever)

Question 6

Epinephrine (Treatment for Hypersensitivity)

Answer 6

• Used to treat anaphylactic shock
• Acts as vasoconstrictor - increases blood pressure
• Only lasts for about 20-30 minutes - time to administer intravenous antihistamines

Question 7

Allergy Shots (Treatment for Hypersensitivity)

Answer 7

• Injected like a vaccine
• Increasing doses of the antigen over a few years
• Induces memory cells that make IgG (instead of IgE)
• IgG will bind and neutralize antigen - before it can bind to IgE – Prevents release of histamine

Question 8

Type 2 Hypersensitivity - AB dependent cytotoxicity

Answer 8

• Antibodies are produced against foreign human cells
  Example 1: Blood Transfusions
  -ABO blood group system - Antibodies target A and B antigens on red blood cells
• Activates macrophages and triggers complement to kill the cells
  Example 2: Hemolytic Disease of the Newborn
• Another surface antigen on red blood cells -Rh factor
• When a child is produced between a Rh- female and an Rh+ male:
  1) Child has 50% chance of being Rh+
  2) Mother can make antibodies against Rh+ blood cells - can attack blood cells of the second child

Question 9

Type 3 Hypersensitivity - Immune Complex Formation

Answer 9

• Occurs at certain antibody to antigen ratios in blood
• Ab forms small complexes with Ag - get trapped in membrane between cells
• Can activate complement
  Results in inflammation
  Activates neutrophils to release enzymes - damage cells

Question 10

Type 4 - Delayed Hypersensitivity

Answer 10

• Cell mediated response (T cells)
• Not Ab mediated
• Causes a delayed reaction 24-72 hours after contact
• Time for T cells to migrate to area
• Ex. Contact dermatitis

Question 11

Type 4 (How it happens)

Answer 11

1) Small chemicals interact with skin proteins to form an antigen
2) Causes a change in skin cells
3) Cell mediated immune response:
-Tc cells are activated to destroy the altered skin cells
- Causes red, itchy, swelling skin
Example: Poison Ivy

Question 12

Transplantation - Tissue or Organ Rejection

Answer 12

• Involves a cell mediated response against antigenically different MHC molecules – Attacked by Tc and NK cells
• Successful transplants require:
  1) Closely matched tissues
  2) Drugs that suppress the immune response (Cyclosporin)
• Because immune system is suppressed transplant patients are very susceptible of infection - Kept in isolation

Question 13

Graft vs Host Disease

Answer 13

• Often occurs after bone marrow transplants

- Tc cells from donor tissue see that host’s body as foreign and attack

Question 14

Autoimmune Disease

Answer 14

• The body has an immune response against itself
• Can occur in response to an infection
• May be genetic (inherited)
• In many cases, the cause unknown

Question 15

Rheumatoid Fever

Answer 15

• Example of an Autoimmune Disease
  -Occurs that strep throat infection
• Antibodies are produced against Streptococcus M proteins.
  Very similar to heart muscle proteins
  Ab attack the heart - cause tissue damage

Question 16

Rheumatoid Arthritis

Answer 16

• Example of an Autoimmune Disease
• IgM, IgG and complement act against collagen in the joints
• Causes chronic inflammation and joint pain

Question 17

Lupus

Answer 17

• Example of an Autoimmune Disease
• Ab produced to chromatin - complex of protein, DNA and RNA
• Chromatin - Ab complexes accumulate in blood vessels, joints, kidneys

Question 18

Multiple Sclerosis

Answer 18

• Example of an Autoimmune Disease
• T cells and macrophages attack the myelin sheath covering nerves
• Symptoms range from mild fatigue to serve paralysis
• May be triggered by infection with Epstein virus

Question 19

Immunodeficiency Disorders

Answer 19

• Results in an inadequate immune system
• Two types:
  1) Primary Immunodeficiency
  2) Acquired

Question 20

Primary Immunodeficiency

Answer 20

• Congenital, Inherited
• Ex. Severe combined immunodeficiency (SCID)
• Non-functional B and T cells
• Allows severe infections

Question 21

Acquired

Answer 21

• Ex. Acquired immunodeficiency syndrome (AIDS)
• Last stage of HIV infection
• HIV infects and kills the Th cells macrophages and dendritic cells
• Patient extremely susceptible to infection - both antibody mediated and cell mediated immune response is impaired