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Medsci 203 (my own) > L13 Hypersensitivity > Flashcards

L13 Hypersensitivity Flashcards

1
Q

What are the primary and secondary responses of the immune system?

A

Primary: First encounter with organism
Secondary: Sebsequent response with the same organism

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2
Q

What are dendritic cells?

A

Dendritic cells are antigen presenting cells residing in tissues.

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3
Q

What do dendritic cells do?

A

They take up antigens, become activated, and migrate to lymph nodes. Mature cells present the antigen-derived peptides on cell surface MHC molecules to activate T cells that recognise the MHC/protein combination

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4
Q

Which cells make up granulocytes?

A

Neutrophils, basophils, eosinophils, mast cells

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5
Q

What do neutrophils do?

A

Phagocytosis and degranulation
Most common WBC, can cause host damage, characterised by its nuclear lobes.

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6
Q

What do basophils do?

A

Degranulation contributes to allergic response

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7
Q

What do Eosinophils do?

A

kill parasites

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8
Q

What do monocytes look like and what do they do?

A

Large cells, horse-shoe nuclei
Phagocytosis and cytokine production, can differentiate into macrophages

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9
Q

What do macrophages do?

A

Antigen-presenting cells, oval nucleus, functionally heterogenous (can change function)

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10
Q

What are the adaptive cells?

A

T and B cells,, plasma cells, and natural killer cells

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11
Q

What are T and B cells characterised by?

A

They have a higher [nuclear] : [cytoplasm] ratio

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12
Q

What do plasma cells do?

A

Produce antibodies, differentiated from B cells, and have lots of mitochondria

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13
Q

What do natural killer cells do?

A

Cytolysis, cytokine production, has secretory lysosomes, punch holes in cells.

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14
Q

Describe the antibody structure

A
  • 2 heavy and 2 light chains held together by disulphide bonds
  • 2 antigen binding sites (light chain)
  • Fc region: constant region, cell receptor binding
    Fc receptor: receptor found on innate immune cells which bind to the Fc region.
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15
Q

What is hypersensitivity?

A

The exaggerated/inappropriate response by the immune system - mediated by IgE, IgM, and IgG, causing damage to your own body.

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16
Q

What does the isotope (variant) of the antibody determined by?

A

The heavy chains of the antibody.

17
Q

What is the original antibody isotope?

A

IgM

18
Q

What is atopy?

A

Atopy is the tendency to develop allergic diseases

19
Q

What are the predisposing factors favouring atopic phenotype?

A

Genetic + environmental determinants –> triggering events –> clinical atopy upon exposure to allergen.

20
Q

What are the genetic determinants favouring atopy?

A
  • Certain alleles of HLA class II genes, PRR genes, pro-inflammatory response genes.
  • Monozygotic (identical) twins are more likely to develop the same allergy than dizygotic twins
21
Q

What are the environmental determinants favouring atopy?

A
  • Excessive hygeine, decreased exposure from farm antigens, pollutants, antibiotics and vaccinations as an infant.
22
Q

What are the triggering events of atopy?

A
  • Flare ups of chronic illness, acute pathogen exposure, emotional stress, hormone fluctuations, and nutritional deficiency.
23
Q

What is type 1 hypersensitivity mediated by?

A

IgE mediated, mast cell degranulation has many effects depending on the route of allergen entry.

24
Q

What and where are the effects of hypersensitivity type 1 depending on route of entry?

A

gastrointestinal tract -> diarrhea, vomitting

eyes, nasal passages, and airways -> decreased airway diameter and increased mucus secretion, congestion and blockage of airways, swelling in nasal passages, ocular itching and sneezing

blood vessels -> increased blood flow, increased permeability, increased fluid in tissues causing greater flow to lymph nodes, increased effector response, hypotension potentially leading to anaphylactic shock.

25
Q

What is the time span in which the allergic reaction happens with type 1 hypersensitivity?

A

1-30 mins

26
Q

What are the mechanisms of type 1 hypersensitivity?

A

IgE-mediated HS, immediate HS allergy, atopy

Allergens cross-link IgE FceR receptors bound on mast cells and induce degranulation.

27
Q

What are some examples of type 1 hypersensitivity (disease names)?

A

Hayfever, asthma, food allergies, hives, anaphylaxis (peanuts and bee stings), etc.

28
Q

What are the two effector stages (when it detects IgE and degranulates) in hypersensitivity type 1?

A

Immediate - fast response within minutes, degranulation of mast cells

Late - redness and swelling (oedema) due to arrival of other cells such as neutrophils, lymphocytes, eosinophils, vasoactive chemotactic comounds (around 4.6 hrs after exposure)

29
Q

What is type 2 hypersensitvity reaction mediated by? Time frame?

A

IgG or IgM antibodies, 5-8 hours after exposure

30
Q

What is the mechanism of type 2 hypersensitivity?

A

Direct, antibody-mediated, cytotoxic HS.

IgG or IgM binds to cell surface of antigens and antibody opsonised cells (complement activation) are recognised by leukocytes through Fc receptors, leading to phagocytosis or killing through antibody-dependent cell-mediated cytotoxicity (ADCC).

31
Q

What are the associated diseases related to type 2 hypersensitivity?

A

Often organ specific antibodies, goodpasture’s syndrome, haemolytic anaemia

32
Q

What is type 3 hypersensitivity induced by? Time frame?

A

IgG or IgM, 4-6 hrs.

33
Q

What is the mechanism by which type 3 hypersensitivity works?

need to watch yt video

A

Immune complex-mediated HS

Antibodies bind antigens in the blood by cross-linking and lodge in small vessels. Insoluble immune complexes enter tissues such as kidneys and drives inflammation and tissue destruction.

34
Q

What are diseases associated with type 3 hypersensitivity?

A

Arthus reaction, aspects of rheumatoid arthritis, and systemic lupus erythematosus (SLE).

35
Q
A
36
Q
A

Medsci 203 (my own) (18 decks)

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