Test 2: Hypersensitivities

Question 1

What are the different types of hypersensitivities?

Answer 1

type I, type II, Type III: antibody mediated
- type I:
- type II:
- Type III:

type IV: T cell mediated
ex: poison ivy

Question 2

How does systemic anaphylaxis (type I) hypersensitivity work?

Answer 2

• reaction of happen molecule with pre-existing IgE antibodies bound to surface of mast cells
• release histamine

Question 3

What are haptens?

Answer 3

• small molecules that can’t elicit immune response by themselves but do so after binding to larger proteins/cells

Question 4

What is the Type 1 Acute phase?

Answer 4

• 5-30 minutes
• vasodilation, vascular leakage (edema), smooth mm spasm which can lead to closing airway

Question 5

What is the Type II Late phase?

Answer 5

• 2-24 hours
• involves other cells other than histamine

Question 6

What to know about Type I hypersensitivities?

Answer 6

• rapid immune rxn
• performed antibodies IgE to allergen
• IgE binds to FceRI on mast cells
• allergen crosslinks bound IgE molecules and triggers release of vasoactive mediatiors- histamine
• acute (less than 1 hr) and late (2 hr- days) phases
• local or systemic (anaphylaxis)

Question 7

What is histamine produced by?

Answer 7

mast cells, basophils, platelets

Question 8

IF you have more IgE bound to mast cells, will you have more or less reaction to allergies?

Answer 8

more reaction to allergies with more IgE

Question 9

What are type II hypersensitive cause by?

Answer 9

IgG or IgM antibodies (reaction with antigens on cells or basement membranes)

Question 10

Which hypersensitivity is responsible for for many antibody-mediated autoimmune diseases?

Answer 10

type II hypersensitivity

Question 11

What antigens are involved in type II hypersensitive?

Answer 11

• foreign antigens (haptens)
• pathogen antigens that cross react with self antigens
• alloantigens (wrong blood group)
• own antigens

Question 12

What is the complement dependent type of type II hypersensitivity?

Answer 12

• opsonization for digestion by macrophages

Question 13

How do antibodies cause tissue damage in type II hypersensitivity?

Answer 13

• reaction of autoantibodies with basement membrane
• complement activation
• anaphylatoxin production
• recruitment of leukocytes
• degranulation, production of ROS
• tissue damage

Question 14

What is the difference between type II and Type III hypersensitivities?

Answer 14

• Type III antibodies bind soluble antigens and complexes deposit in tissue
  ex: lupus

Question 15

What antigens are involved in Type III hypersensitivities?

Answer 15

• autoantigens
• pathogen antigens
• tumor antigens
• foreign proteins
• environmental antigens

Question 16

What is type IV hypersensitivity mediated by?

Answer 16

antigen specific T cells
- both CD4 and CD8 may be involved

Question 17

How does contact hypersensitivity work?

Answer 17

antigens act as haptens and modify host proteins and T cells react (CD4 and CD8)