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Year 2 Foundation in Clinical Practice 2 > HYPERSENSITIVITY REACTIONS > Flashcards

HYPERSENSITIVITY REACTIONS Flashcards

1
Q

how many CLASSES OF HYPERSENSITIVITY REACTIONS and name them

A

4
type 1
type 2
type 3
type 4

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2
Q

hypersensitivity reactions

A

reactions are exaggerated or inappropriate immune responses to harmless substances, leading to tissue damage

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3
Q

type 1 hypersensitivity reactions

A

aka immediate hypersensitivity

caused by IgE antibodies binding to allergens, triggering mast cells and basophils to release histamine.

Examples: Allergies, asthma, anaphylaxis.

note that in some cases people with this type lose it as they get older

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4
Q

type 2 hypersensitivity reactions

A

aka cytotoxic hypersensitivity

caused by IgG or IgM antibodies targeting antigens on cells, thereby activating the complement system, leading to cell destruction.

Examples: Hemolytic anemia, transfusion reactions.

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5
Q

type 3 hypersensitivity reactions

A

aka immune complex hypersensitivity

caused by Antigen-antibody complexes deposit in tissues, causing inflammation.

Examples: Lupus, rheumatoid arthritis

involves IgM, IgG and sometimes IgA antibodies

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6
Q

the most common hypersensitivity reactions

A

type 1 and 4

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7
Q

type 4 hypersensitivity reactions

A

aka delayed-type hypersensitivty

caused by T-cell mediated response, usually 24-72 hours after exposure.

Examples: Contact dermatitis, tuberculosis skin test.

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8
Q

allergens that cause type 1 hypersensitivity can be harmless and more harzadous, true or false

A

true

pollen, dust, drugs, or insect venoms etc could all cause it

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9
Q

anaphalyxis vs prophalyxis

A

A severe, life-threatening allergic reaction that occurs rapidly after exposure to an allergen, causing symptoms like difficulty breathing, swelling, and a drop in blood pressure

while

A preventive treatment or measure taken to prevent disease or a medical condition, such as vaccines or medications to prevent infections or allergic reactions.

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10
Q

some of the effects of type 1 hypersensitivity(what could it lead to)

A

Nasal allergic rhinitis or hay fever

Ocular allergic conjunctivitis, potentially due to seasonal allergens such as pollen or mould spores

Dermatological hives, atopic eczema, or erythema

Soft tissue angioedema

Pulmonary reactions, such as allergic asthma or hypoxia

Systemic reaction, which is a life-threatening medical emergency, and also known as anaphylaxis.

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11
Q

some of the risk factors for type 1 hypersensitivity

A

geographical distribution

environmental risks such as pollution

socioeconomic status

genetic predisposition

“hygiene hypothesis”.

hygiene hypothesis suggests that our modern society practices of good hygiene
and the lack of early exposure to many microbes or antigens may result in failures of
the immune system functionality.

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12
Q

the two stages in the response to an antigen exposure

A

the sensitization stage: host experiences an
asymptomatic contact with the antigen

the effect stage: the pre-sensitized host is re- introduced to the antigen, which then leads to a type I anaphylactic or atopic immune response.

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13
Q

describe IgE mediated mast cell activation and degranulation

A

Sensitization: Upon first exposure to an allergen (e.g., pollen, dust), B cells produce IgE antibodies specific to that allergen. These IgE antibodies bind to FcεR receptors on the surface of mast cells and basophils, which become “sensitized.”

Re-exposure to Allergen: During subsequent exposure to the same allergen, the allergen cross-links the IgE antibodies bound on the mast cell surface.

Mast Cell Activation: The cross-linking of IgE receptors triggers mast cell activation, leading to intracellular signaling.

Degranulation: Activated mast cells release pre-stored granules containing histamine, cytokines, and other inflammatory mediators into the surrounding tissue.

Allergic Reaction: The released mediators cause vasodilation, increased vascular permeability, smooth muscle contraction, and mucus production, leading to symptoms like itching, swelling, and in severe cases, anaphylaxis.

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14
Q

eicosanoids

A

lipid-based signaling molecules that regulate a variety of physiological responses, including inflammation, tissue homeostasis, and host defense

examples are prostaglandins, thromboxanes and Leukotrienes

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15
Q

atopy

A

the tendency to produce an exaggerated IgE immune response to otherwise harmless substances in the environment.

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16
Q

normal IgE levels precludes(preevents) atopy, true or false

A

false

even though atopy is characterised by elevated igE levels, it does not normal levels means there is no atopy

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17
Q

risk factors for atopy

A

family history
high IgE levels
genetics

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18
Q

activation of mast cells may lead to some diseases, name some

A

Hayfever
Allergic Rhinitis
Asthma
Conjunctivitis
Eczema
Dermatitis
Vomiting
Diarrhoea

19
Q

the nasal discharge from allergic rhinitis is often rich in which type of WBC

A

eisinophils

20
Q

eisinophil function

A

Eosinophils are released during infections, allergic reactions, and asthma. They consume harmful matter, and swarm inflamed sites to fight disease

21
Q

food allergies are characterised by

A

activation of mucosal mast cells in the GI tract

Transepithelial fluid loss and increased smooth muscle contraction
causes nausea and diarrhoea in food allergies

22
Q

acute urticaria

A

a skin condition that causes itchy, raised, red, and swollen areas on the skin

it Follows the subcutaneous
administration of allergen
eg. Insect bite

23
Q

does the route of entry of an allergen define it’s clinical effect on the person?

A

yes it does

24
Q

how/when does systemic anaphalyxis occur

a severe, potentially fatal allergic reaction that affects multiple organ systems

A

after intravenous or rapid oral absorption or administration of allergen

25
Q

the effects of systemic anaphalyxis

A

Connective tissue mast cells associated with all blood vessels become activated

Results in vascular permeability (loss of blood pressure, oedema)

airway constriction

swelling of epiglottis

suffocation

26
Q

causes of systemic anaphalyxis

A

Foreign serum
Penicillin injection
Bee venom
Some foods

27
Q

anaphalytic shock

A

a severe, potentially life-threatening allergic reaction that can affect the entire body

it is a response to allergens that** directly ** enter the blood. in this response, mast cells and basophils are enlisted throughout the body

28
Q

treatment for anaphalytic shock

A

adrenaline

its the first line treatment, and causes bronchodilation, which helps with the wheezing..etc associated with A.S, and causes vasoconstriction, to counter the extreme low BPs in A.S

29
Q

name some clinical tests for allergy

A

Skin prick tests

RASTs (Radio Allergo Sorbant Test)

30
Q

how does the Radio Allergo Sorbant Test(RAST) work in testing for allergies

A

Blood sample collected

the potential allergen is attached to a solid phase, which could be a paper disk or a plastic surface

the blood sample is then added to the solid phase, if person allergic to the allergen, then IgE antibodies specific to that specific allergen will be produced

A secondary antibody tagged with a radioactive isotope is added. This secondary antibody binds to any IgE attached to the allergen

these are then counted to quantify the presence of IgE antibodies, indicating the severity of the allergy

note that this test is a bit old and has been largely replaced by tests like immunocap

31
Q

name some treatments for allergies

A

avoiding the allergens
hyposensitization
corticosteroids
antihistamines
etc

Hyposensitization, also known as desensitization or allergen immunotherapy, is a medical treatment for asthma and environmental allergies. It involves gradually exposing a patient to larger and larger amounts of an allergen to change the immune system’s response

there’s loads, check workshop book, you’d have made notes about them in there

32
Q

hyposensitization

A

a long term treatment for allergies, which works by gradually exposing the patient to increasing amounts of the allergen over time, which helps the immune system become less sensitive to it.

aka allergy immunotherapy

33
Q

the two MAIN antibodies involved in hyposensitization, and what they do

A

IgG and IgE
IgE production is reduced, while IgG binds to the allergen before it reaches IgE, blocking it from causing a severe allergic response

34
Q

type 2 hypersensitivity reactions

A

Antibody-mediated immune reaction in which antibodies (IgG or IgM) are
directed against cellular or extracellular matrix antigens.

Results in cellular destruction, functional loss, or tissue damage

35
Q

name some common type of type 2 hypersensitivity reactions

A

Blood transfusion reactions

Hemolytic disease of the newborn (Rh disease; mother Rh- and infant Rh+)

Autoimmune hemolytic anaemias

Drug reactions

Drug-induced loss of self-tolerance

Hyperacute graft rejection

Myasthenia gravis (acetylcholine receptor)

36
Q

name some ways/mechanisms in which damage to cells occur in type 2 hypersensitivity reactions

A

Antibody binding to cell surface receptors and altering its activity

Activation of the complement pathway

Antibody dependant cellular cytotoxicity

37
Q

ADCC
(Antibody Dependent Cellular Cytotoxicity)

usually carried out by IgG

A

an immune response mechanism in which immune cells target and destroy infected or abnormal cells (like cancer cells) that have been marked or coated by specific antibodies.

key in getting rid of abnormal cells

38
Q

main antibodies involved in blood group compatibility are

A

mainly IGM antibodies, but in some cases they could be IgG

39
Q

what happens during incompatible blood transfusions , i.e where the blood of the donor and the receipient are not compatible

note this is in vivo

A

In an incompatible transfusion, IgM antibodies bind to the donor RBCs, activating the complement system, which leads to cell lysis (destruction). Simultaneously, antibody-antigen(ab-ag) complexes are recognized by tissue-fixed macrophages, leading to phagocytosis and further tissue damage.

40
Q

the name of the in vitro test used to detect antibodies on the surface of RBCs before transfusion

these antibodies act agaisnt antigens on the surface of the RBCs, eg if a person with blood type A has in incompatible blood type tranfused to them, then specific antibodies are produced against the donor blood

A

the antoglobulin test or Coomb’s test

Direct Coomb’s Test (DCT): Uses Coomb’s reagent to detect antibodies already attached to red blood cells. Helps diagnose autoimmune hemolytic anemia, transfusion reactions, or hemolytic disease of the newborn.

Indirect Coomb’s Test (ICT): Uses Coomb’s reagent to detect free antibodies in the plasma. Used for blood compatibility testing before transfusions or organ transplants.

41
Q

describe the ABO blood group system, and the main antigens involved in this system

A

The ABO blood group system is based on the presence or absence of certain antigens on the surface of red blood cells (RBCs). These antigens are carbohydrates that are attached to proteins or lipids on the RBC membrane.

the main antigens are A and B antigens

42
Q

name the various blood types and their genotypes(i.e their alleles)

A

Blood group A-> AA or AO

Blood group B-> BB or BO

Blood group AB-> AB

Blood group O-> OO

the genotypes indicate the alleles they inherited from each parent

43
Q

the antiodies contained in the serum of each of the blood types and what they indicate

A

for blood group A, it has anti-B antibodies, indicating that people with blood group A cannot not receive blood from those with B

for blood group B, they have anti-A antibodies, same implies

for blood group O, they have Anti-A and Anti-B antibodies.

AB blood group does not have any antibodies. O is the universal blood group, so can donate to any blood type. AB is the universal receipient

Giving a recipient blood with incompatible antigens can result in a hemolytic transfusion reaction, where the antibodies in the recipient’s blood attack the donor’s red blood cells, leading to cell lysis and serious complications

44
Q
A

Year 2 Foundation in Clinical Practice 2 (9 decks)

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