Immunology 2 Flashcards by Sereen Feroz

Describe the 4 types of hypersensitivity reactions

Type 1 – IgE mediated drug hypersensitivity
Type 2 – IgG mediated cytotoxicity
Type 3 – Immune complex deposition
Type 4 – T cell mediated

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Describe the process Type 1 Hypersensitivity reaction

Needs prior exposure to antigen/drug
IgE antibodies formed after exposure to molecule
IgE becomes attached to mast cells/leucocytes, expressed as cell surface receptors

Re-exposure cause mast-cell degranulation and releases inflammatory tings like histamine, prostaglandins, leukotrienes, platelet activating factor

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Describe some signs/symptoms of Anaphylaxis

Rapid onset
Breathing difficulty, wheeze, cough, SOB
Hypotension
Circulation problems - low BP, high HR
Rash/Hives (itchiness)
Swelling of lips, tongue, throat
Loss of consciousness
Cyanosis

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How common is it to have a biphasic response with anaphylaxis?

1-20% of people have biphasic response

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Describe the process of a Type 2 Hypersensitivity reaction

Antibody dependent
Drug/Metabolite combines w/ protein
Body treats it as foreign and forms antibodies (IgG, IgM)

Antibodies combine w/ antigens
Complement system activates, damages cells

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Describe the process of a Type 3 Hypersensitivity reaction

Immune complex mediated
Antigen/antibody forms large complex and activates complement system
Small blood vessels damaged/blocked

Leucocytes attracted to site of reaction
They release inflammatory substances

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Example of a Type 3 Hypersensitivity reaction

Glomerulonephritis
Vasculitis

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Example of Type 1 H reaction

Anaphylaxis

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Example of Type 2 H reaction

Haemolytic anaemia
MS
Pemphigus

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KEY symptoms of Anaphylaxis?

ABC PROBLEMS
AIRWAY
BREATHING
CIRCULATION

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Describe the process of Type 4 Hypersensitivity reaction

Lymphocyte mediated
Antigen specific receptors develop on T lymphocytes
Leads to local/tissue allergic reaction

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Example of Type 4 H reaction

Contact dermatitis
Stevens Johnson syndrome

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Treatment of Anaphylaxis

Basic life support (ABCDE!!)
Stop drug if infusion

IM ADRENALINE 500MG
(300mg in epipen)

High flow O2
IV fluids - to ↑ BP

If no response after 5 mins, do IM again

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What blood test can you do to confirm anaphylaxis?
When would this test be done?

Mast cell tryptase
AFTER treatment, otherwise Px will die

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Difference between Immune and Non-immune anaphylaxis

NON-immune is due to direct mast cell degranulatin
No prior exposure
but clinically identical

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What does adrenaline do?

Vasoconstriction - ↑ Peripheral vascular resistance, ↑ BP, ↑ Coronary perfusion
VIA alpha-1

Stimulates Beta-1 positive ionotropic and chronotropic effects on heart

↓ Oedema and bronchodilates VIA beta-2

Releases further mediators from mast cells and basophils by ↑ Intracellular c-AMP
∴ ↓ Release of inflammatory mediators

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RF for hypersensitivity reaction

F
EBV, HIV
Prev drug reactions
Uncontrolled asthma
Medication (w/ macro molecules)
Certain HLA groups
Acetylator status

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What are the clinical criteria for an allergy to drug

No correlation with pharmacological properties of drug
No linear relation w/ dose (Even a tiny amount will cause anaphylaxis)
Has a primary exposure
Small number of patients
Happens on re-exposure

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Give examples of polymorphonuclear leukocytes

Neutrophils
Eosinophils
Basophils

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Give examples of mononuclear leukocytes

Monocytes
T-cells
B-cells

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What is the key role of monocytes?

Plays important role in innate and adaptive immunity (phago and Ag presentation)
Removes foreign or dead bodies

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What are the 2 main intracellular granules in neutrophils?

Primary - kills microbes by secreting toxic substances
&
Secondary

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What are neutrophils involved in?

Play important role in innate immunity (phagocytosis)

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Where do macrophages reside?

Reside in tissues
e.g. Kupffer cells in liver, microglia in brain

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What is the approx lifespan of macrophages?

Months/years

Main role of macrophages?

Remove foreign bodies and self (dead/tumour cells) Presents Ag to T-cells

Approx lifespan of eosinophils

8-12 days

What dye is used to stain eosinophil granules?

Acidic dyes (eosin)

Main role of eosinophils?

Activates neutrophils Induces histamine release from mast cells and provokes bronchospasms Mainly associated with parasitic infections and allergic reactions

Lifespan of basophils?

~2 days

How are basophils involved in allergic reactions?

IgE binds to receptors Causes de-granulation releasing _histamine_

What type of dye is used to stain basophil?

Basophil granules stain with **basic dyes**

Basophils are very similar to?

Mast cells

Where are mast cells found? Where is their precursor found?

Only in tissues Precursor in blood

How are mast cells involved in allergic reactions?

IgE binds to receptors Causes de-granulation releasing _histamine_

T-cells play a major role in

Adaptive immunity

Lifespan of T-cells

Hours-years

Where do T-cells mature?

Thymus

Where can T-cells be found?

Blood, lymph nodes and spleen

What are the 4 types of T-cells? Brief description of their function

**T helper 1** - CD4 - helps immune response for intracellular pathogens **T helper 2** - CD4 - helps produce antibodies against extracellular pathogens **Cytotoxic T cell** - CD8 - kills cells directly **T regulator** - regulates immune response

Lifespan of B-cells?

Hours-years

Where do B-cells mature?

Bone marrow

B-cells recognise

Antigens presented by antigen presenting cells (APC)

B-cells differentiate into

Plasma cells that make antibodies

Where are B-cells found?

Blood, lymph nodes and spleen

Natural killer cells account for ___ of __

15% of lymphocytes

Where are Natural killer cells found?

Spleen, Tissues

How do natural killer cells kill?

Via apoptosis

What do natural killer cells kill?

Virus infected cells Tumour cells

Are Immunoglobulin's soluble?

Yes

Name the 5 classes of Igs

IgG IgA IgM IgD IgE

Describe the characteristics of IgG

Predominant in human serum 70-75% of IgG in serum Crosses placenta

Difference between mast cells and basophils

Mast cells are fixed in tissue Basophils can circulate in blood around body

Mast cells express ____

High affinity IgE receptors

Describe the characteristics of IgA

15% of Ig in serum Predominant in mucous secretions e.g. saliva, milk, bronchiolar secretions

Describe the characteristics of IgM

10% of Ig in serum Mainly found in blood Mainly primary response, initial contact w Ag

Why can't IgM cross the endothelium?

Too big

Describe the characteristics of IgD

1% of Ig in serum Transmembrane monomeric form present on mature B cells

What is IgE associated with?

Allergic response and defence against parasitic infections

Define epitope

The part of antigen that binds to antibody/receptor binding site

Define affinity

Measure of binding strength between an epitope and an antibody binding site. Higher the affinity, the better

What do interferons (IFN) do?

Induce a state of antiviral resistance in uninfected cells and limits spread of viral infection

What do interleukins (IL) do?

Cause cells to divide, to differentiate and to secrete factors Over 30 types

What do colony stimulating factors (CSF) do?

Involved in directing division and differentiation on bone marrow stem cells (precursors of leukocytes)

What does tumour necrosis factor do?

Mediate inflammation and cytotoxic reactions

Describe innate defence mechanisms

1st line of defence Provides a barrier to antigens Present from birth No memory DOES NOT require lymphocytes

Describe adaptive (specific) defence mechanisms

Response is specific to antigen Quicker response MEMORY to specific antigen REQUIRES lymphocytes

Give some examples of physiological barriers

Temperature Fever response (inhibits micro-organism growth) pH Gastric acidity

Why are neonates more susceptible to infection than adults? (gastric acidity)

Neonates have a less acidic stomach ∴ more susceptible