W10/11.1

Question 1

what is an antigen?

Answer 1

a molecule capable of inducing an immune response

Question 2

What is the difference between a pathogenic antigen and an allergen

Answer 2

????

Question 3

Hypersensitivity

Answer 3

Exaggerated response to a harmless antigen that results in injury to the tissue, disease, or even death

Question 4

The four types of hypersensitivity

Answer 4

Types 1 - 4

Question 5

Type 1 Hypersensitivity response includes

Answer 5

• IgE immune response to allergen develops- characteristic of atopic individuals
• IgE binds to FcEpsilonR on mast cells and basophils
• Cross-linking of Mast Cell IgE with allergen triggers clinical signs of type I HS

Question 6

Type 1 Hypersensitivity response includes

Answer 6

1: IgE immune response to allergen develops-characteristic of atopic individuals
2: IgE binds to FcEpsilonR on mast cells and basophils
3: Subsequent allergen exposure 2 results in cross-linking of two or more IgE on surface
4: Cross-linking triggers immediate release of preformed mediators- Fast (seconds to minutes)
5: Activated cells also synthesize late mediators (6-8 hrs) from membrane phospholipids

Question 7

Type 1 hypersensitivity phases and mediators

Answer 7

• Immediate release of preformed mediators- Fast (seconds to minutes)
• Activated cells also synthesize late mediators (6-8 hrs) from membrane phospholipids

Question 8

symptoms of type 1 hypersensitivity

Answer 8

• Symptoms depend on tissue/amount of mediators
• Systemic release of histamine: Anaphylaxis
  Allergic asthma (from pollen,…)

Question 9

examples of type 1 hypersensitivity

Answer 9

Localized release of histamine in nasal area or GI tract

• Rhinitis (from pollen,…)
• Food allergies (from nuts,…)

Question 10

Type 1 hypersensitivity testing

Answer 10

• in vivo
• In vitro
• Radio Immuno Sorbent Test (RIST)
• RadioAllergo Sorbent Test (RAST)

Question 11

In Vivo Test (Skin Testing/Patch test)

Answer 11

• Gold standard
• Inject allergen under skin, wheal and flare develop within 15 minutes in sensitized individuals
• Problems:
• Variability (site, lot of allergen)
• Could have severe allergic reaction

Question 12

types of in vitro tests

Answer 12

• less sensitive but usually less traumatic to patient.
• There are 2 in vitro tests:
• RIST: RADIO IMMUNO SORBENT TEST: measurement of total IgE
• RAST: RADIO ALLERGO SORBENT TEST: measurement of antigen-specific IgE.
• Used radioactivity in the past, but non-radioactive Abs used now
  (Mnemotecnic: RIST is for IgE, RAST for Ag- specific IgE)

Question 13

RIST testing

Answer 13

• For total IgE
• Anti-IgE coated on bead/plate + serum IgE + I125anti-IgE
• Nowadays substituted by non- radioactive labeled antibodies

Question 14

RAST testing

Answer 14

• For IgE specific for certain Ag
• Allergen coated on bead + patient serum IgE + I125anti- IgE
• Nowadays substituted by non- radioactive labeled antibodies

Question 15

Type 2 Hypersensitivity (reactant, antigen, mechanism)

Answer 15

Immune reactant : IgG/IgM
Antigen : Cell associated molecule
Mechanism : Complement mediated phagocytosis

Question 16

examples of type 2 hypersensitivity

Answer 16

Transfusion reactions
Hemolytic disease of the newborn (HDN)
Autoimmune hemolytic anemia (including warm and cold autoagglutinins)
Goodpasture’s syndrome
Hashimoto’s disease
Myasthenia gravis

Question 17

type 2 hypersensitivity testing

Answer 17

Direct test (DAT)
Coomb’s
indirect test

Question 18

DAT test

Answer 18

• Need baby’s blood

- Detects in vivo binding of Ig to RBC

Question 19

Coomb’s test

Answer 19

1. Antiglobulin test (add Anti-IgG + anti-C3b)

2. Followed by anti-IgG alone or anti-C3b alone tests to determine if causative Ig is IgG or IgM

Question 20

indirect test

Answer 20

• Need mom’s serum

- Detects ex vivo binding of Ig to RBC