Allergies And Immunocompromised Hosts Flashcards by Maya White

Define hypersensitivity

The antigen-specific immune responses that are either inappropriate or excessive and result in harm to the host

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What are the 2 phases of allergic reaction?

Sensitisation phase - first exposure

Effector phase - re-exposure gives clinical manifestation eg. Anaphylaxis

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What are the different types of hypersensitivity reactions?

Type 1 - immediate
Type 2 - antibody mediated
Type 3 - immune complex mediated
Type 4 - cell mediated

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Describe type 1 hypersensitivity reactions

Allergies
Caused by environmental non-infectious antigens (allergens)
IgE produced

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Describe a type II hypersensitivity reaction

Antibody mediated
Against tissue antigens
IgG/IgM

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Describe a type III hypersensitivity reaction

Immune complexes mediated

Against soluble antigens

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What is atopy?

Genetic predisposition of an individual to produce IgE against different allergens

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What is a TH1 phenotype?

Less likely to get allergies

Protects against

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Describe the type of person who is most likely to develop a TH1 phenotypes for allergies

Large family
Live near overstock 
Variable GI flora
Low antibiotic use 
High likelihood of getting parasites 
Poorer sanitation 
(Exposed to more things)

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What is the TH2 phenotype for allergies?

IgE production

More likely to develop allergies

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Describe the type of person more likely to develop an allergy

Urban homes
Small families
GI flora is stable - less diverse
High Abx use
Less likely to get parasites
Good sanitation

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Name some common allergens

House dust mites
Animals 
Tree/grass pollens 
Insect venom - wasp/bee stings
Medicines 
Chemicals
Foods

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Describe the basis of clinical cross reactivity

If you allergic to one thing then you are more likely to become allergic to others

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Where are mast cells located?

Next to vessels and in mucosal tissue

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What enzymes are in mast cells?

Tryptase
Chymase
Carboxypeptidase

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What are the toxic mediators of mast cells and what do they do?

Histamine 
Heparin 
Toxic to parasites
Increase vascular permeability 
Vasodilation

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What happens on the first exposure to an allergen?

Antigen specific IgEs start to be made

Coat the mast cells

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What happens on the second exposure to allergens?

Allergen binds to specific IgEs on mast cells

Causes mast cell activation

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What happens when mast cells are activated in the epidermis?

Urticaria (hives)
Itchy rash with reddish flare
Vasodilation

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What happens following deep dermis activation of mast cells?

Angioedema
Non-itchy swelling
Can occur in lips, eyes, tongue and upper resp tract

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What effects does the systemic activation of mast cells have?

Hypotension 
Cardiovascular collapse
Generalised urticaria 
Angioedema
Breathing problems

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What are the 3 rules for anaphylaxis?

Sudden onset of symptoms
Rapidly progressing
At least 2 organ systems involved

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What occurs when mast cells are activated in the lungs?

Bronchoconstriction

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What is the treatment of anaphylactic shock?

IM adrenaline

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How does adrenaline help with anaphylaxis?

Vasoconstriction and increased force of myocardial contraction to increase BP Bronchodilation Inhibits mast cell activation

What do we need to monitor in anaphylaxis?

Pulse BP ECG Oximetry - O2 sats

What percentage of cases will have another anaphylactic response without re-exposure?

20%

How do we diagnosis allergy?

Clinical Hx of atopy, allergens Blood tests - allergic specific IgE, mast cell enzymes Skin prick tests - wheel and flare reactions Challenge tests - for food and drug allergies - risky

How do you manage having an allergy?

``` Allergen avoidance/elimination Education Medic alert identification Antihistamines, steroids Epipens Allergen desensitisation/immunotherapy ```

Describe allergen desensitisation/immunotherapy

Administration of increasing doses of allergen extracts over a period of years Hopefully to become desensitised so no longer allergic to these

Describe a sickle cell crisis

Vaso-occlusive crisis Painful episodes which can be very severe and can last up to a week Caused by blocked blood vessels due to the sickle shaped cells (rigid and sticky)

Approximately how many primary immuno deficiencies are there?

> 300

Why do many PIDs have permanent tissue/organ damage when diagnosed?

Takes a long time to diagnose Often symptoms aren't specific Lots of PIDs

Define immunocompromised

State in which the immune system is unable to respond appropriately and effectively to infectious microorganisms

What are primary immunodeficiencies?

Congenital Due to intrinsic gene defect Missing protein/cell or non-functional components

What is a secondary immunodeficiency?

Acquired Due to an underlying disease/treatment Decrease production/function of immune components OR Increased loss or catabolism of immune components

SPUR infections suggests underlying immune deficiency, what does it stand for?

``` S = severe P = persistent U = unusual (site/microorganism) R = recurrent ```

What is a big warning sign for PIDs?

Family history of PID

What are the limitations of the warning signs for PIDs?

Lack of population based evidence Presentations are all different Non-infectious manifestations

What 3 things in children would lead you to think of PIDs?

Family Hx Failure to thrive Diagnosis of sepsis

What is SCID?

Severe combined immunodeficiency Combined T and B cell problem 15% of all PIDs

65% of PIDs are ...

Antibody deficiencies

Give the most common PIDs

``` Common variable immunodeficiency (CVID) IgA deficiency IgG deficiency X linked agammaglubulinaemia Neutropenia ```

If a PID manifested at the age of <6 months, what type would you expect it to be?

T cell or phagocyte defect

If a PID manifested between the ages of 6 months and 5 years, what type would you expect it to be?

B cell/antibody or phagocyte defect

If a PID manifested at the age of >5 years, what type would you expect it to be?

B cell/antibody or complement defect | Or actually a secondary ID

Which pathologies suggest complement deficiencies and of which part?

Pyogenic infections (C3) Meningitis/sepsis/arthritis (C5-9) Angioedema (C1 inhibitor)

Phagocytic defects tend to be found in which infections?

Skin/mucous infections Deep seated infections Invasive fungal infections

What pathologies may suggest antibody deficiencies?

``` Sinoresp infections Arthropathies GI infections Malignancies Autoimmunity ```

What pathologies may suggest T cell defects?

Failure to thrive Deep skin and tissue abscesses Opportunistic infections

What does it mean if people have a weak IgG response to vaccines?

Their B cells are affected

What do you never give to people with T cell defects?

Live vaccines

How do you manage PIDs?

Supportive - prophylactic Abx, treat infections promptly, nutritional support, CMV negative blood products only, avoid live vaccines Specific - regular immunoglobulin therapy, haematopoietic stem cell therapy

Describe immunoglobulin replacement therapy

``` IgG from many donors Make pt immune to the diseases the donors are immune to Life long treatment Improves quality of life Can be IV or SC ```

Which conditions have we found that immunoglobulin replacement therapy works against?

CVID (common variable) Bruton's disease (XLA) Hyper IgM syndrome

Give examples of things that can cause decreased production of immune components

``` Malnutrition Infection Liver diseases Lymphoproliferative diseases Splenectomy ```

What are the functions of the spleen?

Clears blood-borne pathogens Produces antibodies (IgM, IgG) Splenic macrophages remove opsonised microbes and immune complexes

Give some examples of encapsulated bacteria

H influenzae Strep pneumoniae Neisseria meningitidis

What is OPSI?

Overwhelming post-splenectomy infection | Sepsis and meningitis

What is the management for people without a spleen?

Penicillin prophylaxis Immunisation against encapsulated bacteria a Medic alert bracelet

Why to haematological malignancies increase susceptibility to infections?

Chemo induced neutropenia Damage to mucosal barriers Vascular catheters

What can give a pt an increased loss of immune components?

Protein losing conditions - nephropathy, enteropathy (eg. Crohn's) Burns

Viral and fungal infections suggest which type of immune cell deficiency?

T cell

Bacteria and fungal infections suggest which immune cell deficiency?

B cell Or Granulocyte

Allergies And Immunocompromised Hosts Flashcards

(64 cards)