Immunology Flashcards
Define allergy
Umbrella term for hypersensitivity of the immue system to allergens - proteins that the immune system recognise as foreign and potentially harmful triggering an immune response.
Define atopy
Term used to describe a predisposition to having hypersensitivity reactions to allergens. Refers to the tendency to develop eczema, asthma, hayfever, allergic rhinitis and food allergies.
Define atopy
Term used to describe a predisposition to having hypersensitivity reactions to allergens. Refers to the tendency to develop eczema, asthma, hayfever, allergic rhinitis and food allergies.
Define type 1 hypersensitivity reaction
Typical food allergy - IgE triggered mast cells and basophils to release histamine and cytokine - causes immediate reaction
Define type 2 hypersensitivity reaction
Haemolytic disease of newborn - IgG and IgM activate complement system leading to direct damage to cells.
Define type 3 hypersensitivity reaction
SLE, rheumatoid - Immue complexes accumulate and cause damage to local tissues
Define type 4 hypersensitivity reaction
Organ transplant rejection - hypersensitivity mediated by T cell becoming inappropriately activated
Investigation in allergies
Skin prick - sensitisation = unreliable
RAST
Food challenge
Management of allergies
Avoid allergen
Regular hoovering and sheet changes
Stay indoors
Prophylactic antihistamines
Epi pen
Define anaphylaxis
A life threatening medical emergency - caused by type 1 hypersensitivity reaction to specific antigen - causing airway compromise.
Presentation of anaphylaxis
Urticaria
Itching
Angio-oedema - around lips and eyes
Abdominal pain
Shortness of breath
Wheeze
Swelling of larynx - stridor
Tachycardia
Lightheadedness
Collapse
Management of anaphylaxis
ABCDE
IM adrenaline - repeat at 5 minutes
Antihistamines
Steroids
Investigations in anaphylaxis
Mast cell tryptase within 6 hours of a reaction
Define allergic rhinitis
A condition caused by an IgE mediated type 1 hypersensitivity reaction to environmental allergens in the nasal mucosa - seasonal perennial or occupational
Presentation of allergic rhinitis
Runny blocked and itchy nose
Sneexing
Itchy
Red
Swollen eye
Common triggers for allergic rhinitis
Tree pollen or grass
House dust mites
Pets
Mould
Management of allergic rhinitis
Lifestyle
Oral antihistamines
Nasal corticosteroid sprays
Nasal antihistamines
Define cow’s milk protein allergy
A condition typically affecting infants and young children under 3 involving a hypersensitivity reaction to cows milk . Common in formula fed babies
Presentation of Cow’s milk protein allergy
Before 1 year of age
Becomes apparent when weaning
Bloating
Abdo pain
Diarrhoea
Vomiting
Urticarial rash
Angio-oedema
Cough or wheeze
Sneezing
Watery eyes
Eczema
?anaphylaxis
Management of Cow’s milk protein allergy
Avoid cows milk - including mothers who breast feed
Hydrolysed formulas
Retry on milk ladder every 6 months
Define severe combined immunodeficiency
Most sever condition causing immunodeficiency - almost no immunity to infection caused by a number of different genetic disorders that result in absent or dysfunctioning T and B cells
Presentation of SCID
Persisten severe diarrhoea
Failure to thrice
Opportunistic infection - frequent and severe
Unwell after live vaccines
Omenn syndrome
Causes of SCID
Mutations in the common gamma chain on the X chromosome - X linked inheritance
Define Omenn syndrome
Rare cause of SCID - mutation in RAG1 or 2 that codes for proteins in T and B cells - autosomal recessive
Features of Omenn syndrome
Red scaly dry rash
Hair loss
Diarrhoea
Failure to thrive
Lymphadenopathy
Hepatosplenomegaly
Features of DiGeorge syndrome
CATCH 22
Congenital heart disease
Abnormal faces
Thymus gland incompletely developed
Cleft palate
Hypoparathyroidism - causing hypocalcaemia
22 chromosome affected
