HYPERSENSITIVITY REACTIONS

Question 1

how many CLASSES OF HYPERSENSITIVITY REACTIONS and name them

Answer 1

4
type 1
type 2
type 3
type 4

Question 2

hypersensitivity reactions

Answer 2

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

Question 3

type 1 hypersensitivity reactions

Answer 3

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

Question 4

type 2 hypersensitivity reactions

Answer 4

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.

Question 5

type 3 hypersensitivity reactions

Answer 5

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

Question 6

the most common hypersensitivity reactions

Answer 6

type 1 and 4

Question 7

type 4 hypersensitivity reactions

Answer 7

aka delayed-type hypersensitivty

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

Examples: Contact dermatitis, tuberculosis skin test.

Question 8

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

Answer 8

true

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

Question 9

anaphalyxis vs prophalyxis

Answer 9

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.

Question 10

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

Answer 10

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.

Question 11

some of the risk factors for type 1 hypersensitivity

Answer 11

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.

Question 12

the two stages in the response to an antigen exposure

Answer 12

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.

Question 13

describe IgE mediated mast cell activation and degranulation

Answer 13

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.

Question 14

eicosanoids

Answer 14

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

examples are prostaglandins, thromboxanes and Leukotrienes

Question 15

atopy

Answer 15

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

Question 16

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

Answer 16

false

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

Question 17

risk factors for atopy

Answer 17

family history
high IgE levels
genetics

Question 18

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

Answer 18

Hayfever
Allergic Rhinitis
Asthma
Conjunctivitis
Eczema
Dermatitis
Vomiting
Diarrhoea

Question 19

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

Answer 19

eisinophils

Question 20

eisinophil function

Answer 20

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

Question 21

food allergies are characterised by

Answer 21

activation of mucosal mast
cells in the GI tract

Transepithelial fluid loss and
increased smooth muscle contraction
causes nausea and diarrhoea

Question 22

acute urticaria

Answer 22

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

it Follows the subcutaneous
administration of allergen
eg. Insect bite

Question 23

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

Answer 23

yes it does

Question 24

how/when does systemic anaphalyxis occur

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

Answer 24

after intravenous or rapid oral absorption administration of allergen

Question 25

the effects of systemic anaphalyxis

Answer 25

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

Question 26

causes of systemic anaphalyxis

Answer 26

Foreign serum
Penicillin injection
Bee venom
Some foods

Question 27

anaphalytic shock

Answer 27

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

Question 28

treatment for anaphalytic shock

Answer 28

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

Question 29

name some clinical tests for allergy

Answer 29

Skin prick tests

RASTs (Radio Allergo Sorbant Test)

Question 30

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

Answer 30

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

Question 31

name some treatments for allergies

Answer 31

avoiding the allergens
hyposensitization
corticosteroids
antihistamines
etc

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

Question 32

hyposensitization

Answer 32

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

Question 33

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

Answer 33

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

Question 34

type 2 hypersensitivity reactions

Answer 34

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

Question 35

name some common type of type 2 hypersensitivity reactions

Answer 35

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)

Question 36

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

Answer 36

Antibody binding to cell surface receptors and altering its activity

Activation of the complement pathway

Antibody dependant cellular cytotoxicity

Question 37

ADCC
(Antibody Dependent Cellular Cytotoxicity)

usually carried out by IgG

Answer 37

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

key in getting rid of abnormal cells