Hypersensitivity

Question 1

Type 2 - 4 hypersensitivity reactions

Answer 1

Type 2 and 3 are mediated by IgG antibodies, can be to self or foreign.
Type 2, IgG antibodies, its a self associated antigen. It can activate IgG by compliment activation

Question 2

Type 2 Haemolytic disease

Answer 2

foetal Rh-D positive or negative, applies incompatibility

Applies Type2 hyersensitivity

Question 3

Coombs Test

Answer 3

.

Question 4

Myasthenia Gravis

Answer 4

Type 2 hypersensitivity
IgG antibodies to acetylcholin receptors in skeletal muscle
blocks muscle contraction
muscle weakness and fatigue
treatment: actylecholinesterase inhibitors
immunosupressants

Question 5

Graves disease

Answer 5

Type 2 hypersensitivity

Antibodies have same effect as stimulant, express thyroid response

Question 6

Other type 2

Answer 6

Haemolytic anaemia
penicillin acts as hapten
IgG response to novel antigen
C’-mediated lysis of RBC

Pemphigus
desmoglein antibodies
disruption of epidermal layer

Goodpasture’s syndrome
collagen IV igG antibodies
immune damage to renal glomerulus

Question 7

Type 3 hypersensitivity

Answer 7

Mediated by IgG
IgG in bloodstream/serum
formation of immune complexes
complex binds to platelets
release of histamine increase vascular permeability
imflammation of blood vessels

Question 8

Arthus reaction

Answer 8

Type 3 hypersensitivity
Antigen casuses local immune complexes to form
complex activate complement proteins
IgG binds to local mast cells and other leukocytes
-phagocyte recruitment
-platelet activation (clotting)

Question 9

Systematic Lupus Erythematosus (SLE)

Answer 9

Type 3
anti-dsDNA, anti nuclear antigen (IgG) antibodies
associated with HLA-B8-DR2/DR3 expression
photosensitive butterfly rash, arthralgia, arthritis
inflammation of multiple organs
immune complex deposition

Question 10

Type 4 hypersensitivity

Answer 10

Involves T cells
CD4 or CD8 T cells

Type 4 (delayed type)
CD4 + T-cell mediated
typically caused by exposure to hapten which modifies self protein
prescessed altered peptide stimulates a local T cell CD 4 effector response
local macrophages activated by pro inflammatory cytokines-local inflammation

-sensitising agen (hapten) penetrates skin
-binds and modifies self protein
uptake by local APC
induced Th1 cells migrate to exposure site
-Th1 cells activate (T helper) local keotinocytes
-furthere production of local cyotkines
activation of local macrophages
inflammation-skin lesions

Question 11

Example of Type 4 response

Answer 11

CD4+ , Th1 type response

• Nickel sensitivity
• Ni penetrates dermis
• acts as hapten
• infiltration of dermis with CD4+ Th1-type cells
• local inflammation

CD8+, CTL response

• Poison ivy dermatitis
• pentadecacatechol
• APC processing of altered protein
• local inflammation
• target cell destruction by CD8+ CTL

Question 12

Tuberculin hypersensitivity

Answer 12

Type 4

Mantoux skin test, wait to develop response
mycobacterial PPD antigen chalenge test for pre-exposure to TB

Question 13

Granulomatous hypersensitivity

Answer 13

Type 4
Ganulomas caused by persistence of antigen in tissue macrophage
commonly due to chronic infection - chronic cytokine production
TB = chronic type 1 response
leprosy
schistosomiasis