Allergies

Question 1

Allergy

Answer 1

disease following a response by the immune system to an otherwise innocuous antigen

Question 2

Hypersensitivities

Answer 2

harmful immune responses that produce tissue damage

Question 3

type 1 hypersensitivity reaction

Answer 3

immune reactant: IgE
antigen: soluble
Effector mechanism: mast cell activation
example: allergy,asthma

Question 4

Type II Hypersensitivity

Answer 4

• Type II reactions are the result of antibodies, usually IgG, binding to components of cell membranes or extracellular matrix.
• Can be self-components, or exogenous components
• Self: Goodpasture’s syndrome, antibodies bind to basement membrane collagen type IV, glomerulonephritis in kidney, pulmonary haemorrhage in lung

Question 5

what ca be caused by a penicillin allergy

Answer 5

hemolytic anemia

Question 6

Type III hypersensitivity

Answer 6

caused usually by IgG but sometimes IgM:
• Formation of antibody-antigen complexes is a normal part of immune response.
• Usually cleared by reticuloendothelial system (RES): macrophages, neutrophils in liver spleen and bone marrow that ingest and degrade immune complexes
• Excess immune complex deposition in tissues leads to pathology

Question 7

Type III: sites of immune complex deposition: glomeruli

Answer 7

kidney, filtration process makes it very common site in IC deposition, damage driven by complement activation

Question 8

Type III: sites of immune complex deposition: blood vessel walls

Answer 8

IC accumulate on veins and arteries, causes vasculitis, often seen as skin lesions if close to surface

Question 9

Type III: sites of immune complex deposition: Synovial membranes:

Answer 9

Rheumatoid arthritis, in which the IgG of the immune complexes can become an antigen itself, and IgM Rheumatoid Factor antibodies develop.

Question 10

Type III: sites of immune complex deposition: Skin

Answer 10

common site for IC deposition, causes rashes.

Question 11

Type III: sites of immune complex deposition: systemic sites

Answer 11

in case of Systemic Lupus Erythematosus (SLE) IC deposits in kidney, joints, skin, vasculature, muscle and other organs.

Question 12

Type IV Hypersensitivity

Answer 12

these are entirely cell mediated, Most Type IV reactions are caused by CD4+ delayed type hypersensitivity (DTH) reactions. ‘Delayed’ refers to reaction occurring 2 to 4 days after antigen exposure
• Macrophages that cause damage are not specific, harm infected and non-infected tissue

Question 13

DTH reactions

Answer 13

• Some DTH reactions can be prolonged and damaging
• Listeria, Leishmania, M. tuberculosis, M. Leprae
• DTH responses can lead to walling off infectious sites, granulomas.
• Remnants of granulomas are tubercles seen in longterm tuberculosis

Question 14

Contact sensitivities of DTH reactions

Answer 14

• A special category of DTH reaction in which antigen is not an infectious agent, but a chemical that binds to cell surface.
• Heavy metal sensitivity
• Poison Ivy, reaction in skin to catechols