Hypersensitivity part 2 Flashcards

1
Q

What specific allergies should you include in a history?

A

Patients LIE

  • Latex
  • Iodine
  • Elastoplast
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2
Q

What immune reactant is included in a type 2 hypersensitivity reaction?

A

IgG

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3
Q

How many different types of hypersensitivity reactions are there?

A

4

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4
Q

In which immune reaction is there no antibody involved?

A

Type 4

Driven by T cell activity

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5
Q

Give an example of a type 2 hypersensitivity reaction and how it works

A

Goodpasture’s syndrome, antibodies bind to basement membrane collagen type 4, glomerulonephritis in kidney, pulmonary haemorrhage in lung.

  • 100% have nephritis
  • Around 50% have lung problems
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6
Q

Give an example of a drug which can cause a type 2 hypersensitivity reaction

A

Penicillin

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7
Q

Describe how a type 2 hypersensitivity reaction works

A
  • Binds to proteins that coat the surface of RBC
  • Creates neoepitope
  • This substance is taken up by macrophages/dendritic cells
  • Broken up and presented to T cells
  • Activate specific CD4 T cells to become TH2 cells
  • B cells are activated by antigen and by help from activated TH2 cells
  • Plasma cells secrete penicillin-specific IgG which binds to modified RBC
  • Penicillin-specific IgG binds to penicillin-modified proteins on RBC
  • Activation of compliment components C1-C9 and formation of membrane-attack complex causes lysis of RBC
  • Activation of compliment components C1-C3 leads to covalent bonding of C3b and phagocytosis of antibody - and compliment-coated RBC
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8
Q

What antibodys are involved in type 3 hypersensitivity?

A

IgG but sometimes IgM

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9
Q

What system usually clears antibody-antigen complexes?

A
Reticuloendothelial system (RES):
Macrophages, neutrophils in liver spleen and bone marrow that ingest and degrade immune complexes
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10
Q

How does a type 3 hypersensitivity reaction work?

A
  • Antibody-antigen complexes form and too many are made and not cleared
  • Complement releases inflammatory mediators C5a, C3a and C4a. C5a also induces cell degranu,ation
  • Local inflammation, movement of fluid and protein into tissue and blood vessel is occluded
  • Over the course of 1-2 hrs
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11
Q

What are the common sites of immune complex deposition? (type 3 reaction)

A
  • Glomeruli
  • Blood vessel walls
  • Synovial membranes
  • Skin
  • Systemic sites
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12
Q

In what reaction does compliment not play a role?

A

Type 4

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13
Q

How long does it take for there to be a reaction to type 4 hypersensitivity?

A

2 to 4 days

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14
Q

Describe how a type 4 hypersensitivity reaction works?

A
  • Antigen is introduced into subcutaneous tissue and processed by local antigen-presenting cells
  • A TH1 effector cell recognises antigen and releases cytokines which act on vascular endothelium
  • Recruitment of T cells, phagocytes, fluid, and protein to site of antigen injection causes visible lesion
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15
Q

Give some examples of type 4 / DTH reactions

A
  • Listeria
  • Leishmania
  • M. tuberculosis
  • M. Leprae
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16
Q

What are remenants of granulomas in longterm TB?

A

Tubercles

17
Q

What are contact sensitivities classified as?

A

Delayed Tissue Hypersensitivity Reaction (type 4)

18
Q

What are granulomas?

A
  • Structure formed during inflammation
  • Collection of macrophages
  • Forms when immune system attempts to wall off substances it perceives as foreign but is unable to eliminate
19
Q

Name some contact sensitivities

A
  • Heavy metal
  • Poison Ivy
  • ## Elastoplast
20
Q

Give some examples of type 2 autoimmune reactions

A
  • Autoimmune haemolytic anaemia
  • Autoimmune thrombocytopenic purpura
  • Goodpasture’s syndrome
  • Pemphigus vulgaris
  • Acute Rheumatic fever
21
Q

Give some examples of type 3 reactions

A
  • Mixed essential cryoglobulinemia
  • SLE
  • Rheumatoid arhtritis
22
Q

Give some examples of type 4 hypersensitivity reactions

A
  • Insulin dependant diabetes mellitus
  • Rheumatoid arthritis
  • Multiple Sclerosis
23
Q

Pollen allergy is an example of what type of hypersensitivity reaction?

A

Type 1