ALLERGIC REACTIONS

Question 1

what is an allergic reactions?

Answer 1

• An allergic reactions is a type of immune response
• This response is generated against allergens (antigens) such as peanuts, pollen, dust-mite feces and etc
• Allergies can cause discomfort and distress for the patient
• Not life threatening but can sometimes cause anaphylaxis, a condition that can be fatal

Question 2

using this category, list down the allergic reactions.
1. skin contact
2. injection
3. ingestion
4. inhalation

Answer 2

1. skin contact - poison plants, animal scratches, pollen, latex
2. injection - bee sting
3. ingestion - medication, nuts, shellfish
4. inhalation - pollen, dust, mold and mildew, animal dander

Question 3

There are 4 main types of
hypersensitivity reaction :
type I, type II, type III, type IV.

list down the immune reactant of each type.

Answer 3

type I - IgE
type II - IgG or IgM
type III - IgG and IgM
type IV - T cells

Question 4

list down antigen form of each type.

Answer 4

type I - soluble antigen
type II - cell-bound antigen
type III - soluble antigen
type IV - soluble or cell-bound antigen

Question 5

what is the mechaism of activation and examples of hypersensitivity reactions for type I?

Answer 5

Allergen-specific IgE antibodies bind to mast cells via their Fc receptor. When the specific allergen binds to the IgE, cross-linking of IgE induces degranulation of mast cells.

Local and systemic anaphylaxis,
seasonal hay fever, food allergies, and drug allergies

Question 6

what is the mechaism of activation and examples of hypersensitivity reactions for type II?

Answer 6

IgG or IgM antibody binds to cellular antigen, leading to complement activation and cell lysis. IgG can also mediate ADCC with cytotoxic T cells, natural killer cells, macrophages, and neutrophils.

Red blood cell destruction after transfusion with mismatched blood types or during hemolytic disease of the newborn.

Question 7

what is the mechaism of activation and examples of hypersensitivity reactions for type III?

Answer 7

Antigen-antibody complexes are deposited in tissues.
Complement activation provides inflammatory mediators and recruits neutrophils. Enzymes released from neutrophils damage tissue.

Post-streptococcal glomerulonephritis,
rheumatoid arthritis, and systemic lupus erythematosus

Question 8

what is the effector mechanism in allergic reaction?

Answer 8

• Most IgE is found on the surface of mast cells, basophils and activated eosinophils 🡪 bound there by high-affinity receptors
• Mast cells 🡪 residents of mucosal and epithelial tissues, located in blood vessel, where they guard against invading pathogens and continuously express the IgE
  receptor on their surface

Question 8

what is the mechaism of activation and examples of hypersensitivity reactions for type IV?

Answer 8

TH1 cells secrete cytokines, which activate macrophages and cytotoxic T cells.

Contact dermatitis, type I diabetes mellitus, and multiple sclerosis

Question 9

When a person facing an allergens, the allergens_____

Answer 9

crosslinks with IgE molecule bound to a receptor on a mast cell

Question 10

what does the crosslink causes?

Answer 10

This causes degranulation of the mast cells 🡪 then a
variety of inflammatory mediators are released

Question 11

Some mediators cause :

Answer 11

immediate increases in local
blood flow, vessel permeability and enzyme production
🡪 tissue destruction

Question 12

what does eosinophils do in the effector mechanism in allergic reaction?

Answer 12

• Eosinophils 🡪 found mainly in the connective tissue lying immediately under the respiratory, digestive and genitourinary epithelial

Cause tissue damage and enhance the allergic reactions

Question 13

what are the clinical effects of allergic reactions?

Answer 13

• The clinical effects of allergic reactions vary according to the site of mast-cell activation
• These clinical effects depend on three variables :

1. The amount of allergen-specific IgE present on the mast cells
2. The route by which the allergen is introduced into the body
3. How much allergens enters the body

Question 14

explain mast cell activation and granule releases.

Answer 14

divided into three:

1. gastrointestinal tract - increased fluid secretion and persitalsis causing expulsion of gastrointestinal tract contents (diarrhea, vomitting)
2. airways - decreased diameter, increased secretion of mucus causing congestion and blockage of airways (wheezing, ciughing, phlegm) and swelling and secretion of mucus in nasal passages.
3. blood vessels - increased in blood flow, increased permeability.