Hypersensivity

Question 1

What are the four types of hypersensitivity?

Answer 1

Type I, Type II, Type III, Type IV

Question 2

What is hypersensitivity?

Answer 2

Any inappropriate or excessive immune response that results in bystander damage to the self

Question 3

Define allergy in the context of hypersensitivity.

Answer 3

Immune responses are induced against innocuous exogenous antigens

Question 4

What is autoimmunity?

Answer 4

A harmful immune response directed against self-antigens

Question 5

What roles do allergen, IgE, and mast cells play in Type I hypersensitivity?

Answer 5

Allergen triggers the response; IgE binds to allergens; Mast cells degranulate upon allergen exposure

Question 6

What are the phases of Type I hypersensitivity?

Answer 6

Sensitisation, Early-phase Reaction, Delayed-phase Reaction

Question 7

What cytokines are produced during sensitization in Type I hypersensitivity?

Answer 7

IL-4 and IL-13

Question 8

Fill in the blank: Atopy is a ______ to produce IgE antibody in response to environmental allergens.

Answer 8

[genetic predisposition]

Question 9

Name two common allergens associated with Type I hypersensitivity.

Answer 9

• Pollen
• House dust mite

Question 10

What is the triple vascular response of Lewis?

Answer 10

Response induced by histamine release during allergic reactions

Question 11

What are common causes of systemic allergy or anaphylaxis?

Answer 11

• Bee and wasp stings
• Foods
• Latex rubber
• Drugs

Question 12

True or False: Anaphylactoid reactions are mediated by IgE.

Answer 12

False

Question 13

What is the role of antibodies in Type II hypersensitivity?

Answer 13

Opsonisation, Complement activation, Toxin neutralisation, Antibody dependent cell mediated cytotoxicity (ADCC), Direct antimicrobial activity

Question 14

What happens during the early phase reaction in Type I hypersensitivity?

Answer 14

Mast-cell degranulation occurs due to IgE-allergen interaction

Question 15

What is the mechanism of action for mast cell stabilisers?

Answer 15

Inhibit release of vasoactive mediators

Question 16

What is allergen immunotherapy (AIT)?

Answer 16

Desensitization treatment involving escalating doses of allergen

Question 17

What is the pathophysiology of Type III hypersensitivity?

Answer 17

Immune complex formation due to antigen-antibody interactions

Question 18

Fill in the blank: In Type III hypersensitivity, the antigen-antibody ratio affects ______ formation.

Answer 18

[complex]

Question 19

What is delayed hypersensitivity (DTH)?

Answer 19

The slowest form of hypersensitivity mediated by T cells, taking 2 to 3 days to develop

Question 20

Define haptens in the context of hypersensitivity.

Answer 20

Small molecules that elicit an immune response only when attached to a large carrier such as a protein

Question 21

What are the clinical effects of Type I hypersensitivity?

Answer 21

Can range from mild allergic reactions to severe anaphylaxis

Question 22

What tests are used to investigate allergic diseases?

Answer 22

• Skin prick tests
• Specific IgE tests
• Component resolved diagnostics
• Challenge tests
• Mast cell tryptase

Question 23

What is the significance of the European Academy of Allergy and Clinical Immunology’s recommendation for AIT?

Answer 23

At least 3 years of AIT is recommended to achieve long-term benefits

Question 24

What is the role of Fc receptor bearing cells in Type II hypersensitivity?

Answer 24

Engage in antibody-dependent cell-mediated cytotoxicity (ADCC)

Question 25

What factors influence the formation of abnormal immune complexes in Type III hypersensitivity?

Answer 25

Antigen-antibody ratio and the presence of specific antibodies

Question 26

What are the clinical effects of Type II hypersensitivity?

Answer 26

Can lead to conditions such as hemolytic anemia or transfusion reactions

Question 27

What is the role of Th1 and Th17 cells in Type IV hypersensitivity?

Answer 27

Th1 cells promote cell-mediated immunity; Th17 cells are involved in inflammatory responses

Question 28

True or False: Type IV hypersensitivity is primarily antibody-mediated.

Answer 28

False

Question 29

What is the pathophysiology of immune complex formation in Type III hypersensitivity?

Answer 29

Complexes form when antigens bind with antibodies in circulation

Question 30

What is the slowest form of hypersensitivity mediated by T cells?

Answer 30

Delayed hypersensitivity (DTH) ## Footnote This type can take 2 to 3 days to develop.

Question 31

Define haptens in the context of immunology.

Answer 31

Small molecules that elicit an immune response only when attached to a large carrier such as a protein. ## Footnote The carrier may not elicit an immune response by itself.

Question 32

What are the two phases of Type IV hypersensitivity?

Answer 32

* Sensitisation phase * Effector phase

Question 33

Provide an example of Type IV hypersensitivity.

Answer 33

Nickel hypersensitivity ## Footnote This is a common example of contact dermatitis.

Question 34

What is a common condition associated with Type IV hypersensitivity?

Answer 34

Eczema

Question 35

What diagnostic method is often used for Type IV hypersensitivity?

Answer 35

Patch testing

Question 36

Contrast the mechanisms of which hypersensitivity types?

Answer 36

Types I, II, III, and IV hypersensitivity.

Question 37

List the roles in Type I hypersensitivity.

Answer 37

* Allergen * IgE * Mast cells * Inflammatory cells * Mediators * Cytokines

Question 38

What does atopy refer to?

Answer 38

A genetic predisposition to develop allergic diseases.

Question 39

What are the roles of antibody, complement, Fc receptor bearing cells, and ADCC in which type of hypersensitivity?

Answer 39

Type II hypersensitivity.

Question 40

What is the pathophysiology of immune complex formation in which type of hypersensitivity?

Answer 40

Localized and systemic Type III hypersensitivity.

Question 41

What factors are involved in the formation of abnormal immune complexes?

Answer 41

Various immunological factors.

Question 42

What roles do haptens, carrier proteins, Th1 cells, Th17 cells, antigen presenting cells, and monocytes/macrophages play in which type of hypersensitivity?

Answer 42

Type IV hypersensitivity.

Question 43

True or False: Type IV hypersensitivity is mainly mediated by mast cells.

Answer 43

False ## Footnote It is mainly mediated by CD4 T helper cells and CD8 cytotoxic T cells.

Question 44

What is the most useful investigation in type 1 hypersensitivity?

Answer 44

Skin prick testing.

Question 45

Which clinical feature would be unusual in acute systemic type 1 hypersensitivity?

Answer 45

Eczematous rash