Chapter 17 Immunologic Disorders Flashcards
Hypersensitivity - Allergic Response
- An antigenic response beyond that considered normal
- Immune response to an allergen - An antigen that causes hypersensitivity
Type 1 Hypersensitivity
Anaphylactic Response
Have:
1) First encounter
2) Second encounter
Anaphylactic First Encounter
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
Anaphylactic Second Encounter
- 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)
Antihistamine (Treatment for Hypersensitivity)
- Blocks the action of histamine
- Histamine still produced but cannot trigger inflammation
- Works well for mild symptoms (Ex. Hay Fever)
Epinephrine (Treatment for Hypersensitivity)
- Used to treat anaphylactic shock
- Acts as vasoconstrictor - increases blood pressure
- Only lasts for about 20-30 minutes - time to administer intravenous antihistamines
Allergy Shots (Treatment for Hypersensitivity)
- 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
Type 2 Hypersensitivity - AB dependent cytotoxicity
- 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
Type 3 Hypersensitivity - Immune Complex Formation
- 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
Type 4 - Delayed Hypersensitivity
- 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
Type 4 (How it happens)
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
Transplantation - Tissue or Organ Rejection
- 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
Graft vs Host Disease
- Often occurs after bone marrow transplants
- Tc cells from donor tissue see that host’s body as foreign and attack
Autoimmune Disease
- 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
Rheumatoid Fever
- 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
