Hypersensitivity Flashcards
Type 1 hypersensitivity aka?
Allergy or atopy
T1 hypersensitivity antigen is?
allergen
mechanism of T1 hypersensitivity
- exaggerated Th2 response
- overproduction of IL-4
- Excessive IgE made
- IgE binds masts cells
- When allergen is contacted, mast cells degranulate
Important cytokines in IgE synthesis
IL-4, IL-5 and IL-13
Immediate vs late phase effects of mast cell degranulation
Immediate: effects of granules
Late phase: prostaglandins, leukotrienes (things that need to be made)
IL-33
role in inflammation, promotes Th2 leading to allergy. induces mast cell degranulation. affects smooth muscle, epithelial cells, fibroblasts, keratinocytes, DCs, macrophages
Atopic dermatitis
allergic skin disease, characterized by chronically inflamed and itchy skin. IL-31 blocks pruritus.
Diagnosing T1 hypersensitivity
Preferred: intradermal testing
can also do:
Passive Cutaneous Anaphylaxis, measure IgE levels with ELISA/Western blot
T2 Hypersensitivity aka?
Antibody dependent cellular cytotoxicity
T2 hypersensitivity mechanisms
main: 1) opsonization 2) complement-based destruction Less common: 3) Ab's stop normal function of cell mainly IgG and IgM
Incompatible blood transfusions - which type of hypersensitivity?
Type 2
Hemolytic disease of the newborn
somewhat common in foals. Mare sensitized against fetal blood antigen transfers Ig’s, these destroy fetal blood cells
Bovine Neonatal pancytopenia
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
Type 2 hypersensitivity reaction to drugs
drugs bind to cell surface and create a neoantigen or change a host cell antigen into one that looks foreign
T3 Hypersensitivity aka?
Immune complex-mediated
Local vs systemic T3
Local = complex in tissue Systemic = complex in blood
Severity of T3 determined by?
amount of complexes, site of deposition
Arthus reaction
localized hypersensitivity due to injection of an antigen subQ that the host was previously exposed to
Local T3 diseases
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
General T3 diseases
Serum sickness - reaction to diphtheria treatment with hyperimmune serum
Glomerulonephritis
T4 hypersensitivity aka?
Delayed hypersensitivity
Mechanism of T4 hypersensitivity
A) cytokine-mediated inflammation (IFN-gamma, IL-17), recruitment of macrophages and neutrophils
B) CD8+ killing of host cells
T4 granulomas
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
Allergic contact dermatitis
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
