Hypersensitivity

Question 1

Type 1 hypersensitivity aka?

Answer 1

Allergy or atopy

Question 2

T1 hypersensitivity antigen is?

Answer 2

allergen

Question 3

mechanism of T1 hypersensitivity

Answer 3

1. exaggerated Th2 response
2. overproduction of IL-4
3. Excessive IgE made
4. IgE binds masts cells
5. When allergen is contacted, mast cells degranulate

Question 4

Important cytokines in IgE synthesis

Answer 4

IL-4, IL-5 and IL-13

Question 5

Immediate vs late phase effects of mast cell degranulation

Answer 5

Immediate: effects of granules

Late phase: prostaglandins, leukotrienes (things that need to be made)

Question 6

IL-33

Answer 6

role in inflammation, promotes Th2 leading to allergy. induces mast cell degranulation. affects smooth muscle, epithelial cells, fibroblasts, keratinocytes, DCs, macrophages

Question 7

Atopic dermatitis

Answer 7

allergic skin disease, characterized by chronically inflamed and itchy skin. IL-31 blocks pruritus.

Question 8

Diagnosing T1 hypersensitivity

Answer 8

Preferred: intradermal testing
can also do:
Passive Cutaneous Anaphylaxis, measure IgE levels with ELISA/Western blot

Question 9

T2 Hypersensitivity aka?

Answer 9

Antibody dependent cellular cytotoxicity

Question 10

T2 hypersensitivity mechanisms

Answer 10

main:
1) opsonization
2) complement-based destruction
Less common:
3) Ab's stop normal function of cell
mainly IgG and IgM

Question 11

Incompatible blood transfusions - which type of hypersensitivity?

Answer 11

Type 2

Question 12

Hemolytic disease of the newborn

Answer 12

somewhat common in foals. Mare sensitized against fetal blood antigen transfers Ig’s, these destroy fetal blood cells

Question 13

Bovine Neonatal pancytopenia

Answer 13

Due to vaccine. Get MHC from both parents, but also receive Ab’s from mother against fathers MHC (due to a vaccination). Antibodies will bind leukocytes and bone marrow cells

Question 14

Type 2 hypersensitivity reaction to drugs

Answer 14

drugs bind to cell surface and create a neoantigen or change a host cell antigen into one that looks foreign

Question 15

T3 Hypersensitivity aka?

Answer 15

Immune complex-mediated

Question 16

Local vs systemic T3

Answer 16

Local = complex in tissue
Systemic = complex in blood

Question 17

Severity of T3 determined by?

Answer 17

amount of complexes, site of deposition

Question 18

Arthus reaction

Answer 18

localized hypersensitivity due to injection of an antigen subQ that the host was previously exposed to

Question 19

Local T3 diseases

Answer 19

Blue eye - canine adenovirus type 1 (anterior uveitis leading to edema)
hypersensitivity pneumonitis - inhalation of antigen (ex: s. rectivirgula)
Staphylococcal hypersensitivity - pruritic pustular dermatitis. T1, 3 and 4 may be involved but T3 predominates

Question 20

General T3 diseases

Answer 20

Serum sickness - reaction to diphtheria treatment with hyperimmune serum
Glomerulonephritis

Question 21

T4 hypersensitivity aka?

Answer 21

Delayed hypersensitivity

Question 22

Mechanism of T4 hypersensitivity

Answer 22

A) cytokine-mediated inflammation (IFN-gamma, IL-17), recruitment of macrophages and neutrophils
B) CD8+ killing of host cells

Question 23

T4 granulomas

Answer 23

Granuloma formation - macrophages ingest but fail to kill bacteria. lesion develops around necrotic centre. if proper (Th1) = bacteria die from lack of oxygen, if inadequate (Th2) bacteria can escape

Question 24

Allergic contact dermatitis

Answer 24

T4 pathology
epidermal inoculation. foreign small molecules bind MHC. act as hapten by combining with skin molecules
Important cytokines: IL-12, IL-18, IL-23 –> Th1 and Th17 cells promoting cytotoxicity
Usually in hairless regions