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Immunology > Hypersensitivity reactions II > Flashcards

Hypersensitivity reactions II Flashcards

1
Q

what is type II hypersensitivity also known as

A

cytotoxic hypersensitivty

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2
Q

what are antibodies directed against antigens on

A

SPECIFIC cells/tissues

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3
Q

what antibodies are involved in type II

A

IgM and IgG

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4
Q

2 consequences of antibody binding to cell surface antigen

A

Complement is activated

antibody-dependent cell-mediated cytotoxicity

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5
Q

3 things that happen here once complement is activated

A

cell lysis

deposition of complement components (opsonisation)

macrophage and neutrophil activation (lysosomal content released - damage)

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6
Q

examples of type II hypersensitivty reactions

A

blood transfusion

Haemolytic disease of the newborn

Hyperacute graft rejection

Reactions to tissue antigens

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7
Q

what is Haemolytic disease of the newborn

A

condition that occurs when a mother’s antibodies cross the placenta and attack the red blood cells of her baby. This happens when the mother has a different blood type from her baby, and her immune system produces antibodies against the baby’s red blood cells.

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8
Q

example of a Type II hypersensitivity reaction which is a reaction to tissue antigens

A

Goodpasture’s syndrome (antibodies target basement membrane collagen) - immune system attacks the lungs and kidneys

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9
Q

whats HDN due to

A

rhesus incompatibility

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10
Q

how much of population is Rh+ and Rh-

A

Rh+ = 85%
Rh- = 15%

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11
Q

what antibodies are not normally present in Rh- people

A

antibodies to Rh antigens

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12
Q

what type of antibodies are RH antibodies

A

IgG

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13
Q

what are the antibodies called that are produced by the immune system in response to exposure to Rh-positive red blood cells

A

anti-Rh antibodies

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14
Q

3 effects of anti-Rh antibodies

A

spontaneous abortion

baby born with mild jaundice

baby born with Haemolytic Disease of the Newborn

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15
Q

how to prevent affects of anti-Rh antibodies

A

treat mother with Anti-Rh antibodies (Rhogam) within 72 hours of birth of each Rh+ child

Anti-Rh antibody will bind RBC, before B cell activation (prevents b cell activation and memory cell formation)

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16
Q

Immune complex mediated (type III) hypersensitivity reactions

A

immune complexes form in the bloodstream and deposit in various tissues, leading to inflammation and tissue damage.

immune complexes can deposit in tissues like joints, skin or kidneys

17
Q

when immune complexes are deposited in tissues in type III hypersnesitvity, what happens?

A

immune complexes can activate complement proteins and attract immune cells such as neutrophils and macrophages. These cells release enzymes and toxic substances that can damage surrounding tissues and lead to inflammation, swelling, and pain.

18
Q

e.g. of type III hypersensitivity in persistent infection

A

ab’s form against microbial antigens (chronic hep B - liver infection by hep b virus)

19
Q

e.g. of type III hypersensitivity in autoimmunity

A

Antibodies formed against self antigens

Immune complexes deposited in the kidney, joint, arteries, skin, lungs

20
Q

localised type III reaction example

A

arthus reaction (typically seen in response to the injection of an antigen (such as a vaccine) into a previously sensitized individual. The reaction can manifest as a raised, red, and painful lesion at the site of injection, and may also involve swelling, fever, and tissue necrosis)

21
Q

generalised localised type III reaction example

A

serum sickness - in response to the administration of a foreign protein, such as a medication or antiserum, that triggers the production of antibodies (fever, joint pain, rash, swelling)

22
Q

when does the arthus reaction appear

A

4-8 hours after injection (intradermal, subcutaneous) of an antigen into an animal with high levels of specific circulating antibody

23
Q

3 things arthus reaction leads to

A

Leads to complement activation (C3a, C5a) , mast cell degranulation, neutrophil chemotaxis

24
Q

in arthus reaction what leads to release of lytic enzymes and resultant tissue damage

A

neutrophils unable to phagocytose immune complexes

25
Q

Intrinsic allergic alveolitis (give 2 examples)

A

An occupational disease due to inhalation of immunogenic proteins or spores

Examples :
Farmer’s Lung
mushroom worker’s disease
coffee worker’s disease
cheese worker’s disease

26
Q

what does farmers lung begin with in winter

A

mild cough

27
Q

what causes farmers lung

A

sensitisation to spores of thermophilic actinomycetes which grow in damp hay.

28
Q

what precipiate over time in lungs in farmers lung, which activate complement (inflammation) and cause fibrosis

A

Immune complexes (IgG/antigen)

29
Q

treatment for farmers lung

A

early diagnosis and avoidance
corticosteroids

30
Q

when does delayed type IV hypersensitivity reaction occur

A

when T cells in the immune system react to an antigen, resulting in inflammation and tissue damage

31
Q

how long can delayed type IV hypersensitivity take to develop

A

Takes 12 hours to develop

But can develop within 72 hours or after
weeks of exposure

32
Q

2 things delayed type IV hypersensitivity is mediated by

A

T lymphocytes and macrophages

33
Q

whats the tuberculin test

A

a type of delayed-type hypersensitivity (DTH) test used to determine if a person has been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB)/exposed to BCG vaccine

34
Q

what is contact hypersensitivity

A

Dermatitis caused by exposure to: biological stains, hair dyes, poison ivy, nickel salts, mercuric salts (tattoos)

35
Q

what type of immune response is contact hypersensitivity

A

T-cell-mediated immune response that occurs when the immune system reacts to an allergen.

36
Q

What do t cells release in contact hypersensitivity which recruit eosinophils and mast cells that cause inflammation, itching and redness

A

cytokines

37
Q

Coeliac Disease

A

A chronic condition of the upper small intestine caused by a reaction to gluten (antigen is gliadin)

38
Q

2 consequences of increased t lymphocytes and macrophages in coeliac disease

A

Villous atrophy in small bowel (damaged villi)
malabsorption of food

Immunology (13 decks)

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