Allergy and hypersensitivity Flashcards
what is a type 1 hypersensitivity reaction?
Type I hypersensitivity is an immediate reaction to environmental antigens mediated via IgE
what is atophy?
Atopy is an inherited trait for Type I hypersensitivity
what are allergens?
Allergens are antigens that trigger allergic reactions
what effect does histamine have?
Vasodilatation, increased capillary permeability, chemokinesis, bronchoconstriction
what effect does neutral proteases ( try-gases, chemises and carboxypeptidase A) have?
Increased vascular permeability, airway hyperresponsiveness, cell recruitment
what effect does proteoglycan have?
Binds granule proteases
what effect does neutral proteases such as b-glucosaminidase have?
Activates C3
Splits off glucosamine
what are the main areas exposed to antigens?
skin, gi tract and lungs
what effect do Eosinophil chemotactic factors and Neutrophil chemotactic factors have?
eosinophil chemotaxis
neutrophil chemotaxis
what effect do platelet activating factor have?
mediator release
what effect does IL – 3, 4, 5 & 6 GM-CSF, TNF have?
Macrophage activation, trigger acute phase proteins etc
what newly synthesised product does the lipoxygenase pathway include?
Leukotrienes C4, D4, B4
what is the effect of the lipoxygenase pathway?
Vasoactive, bronchoconstriction, chemotaxis
what is the newly synthesised product in the cycle-oxygenase pathway?
Prostaglandins Thromboxanes
what effect does the cyclo-oxygenase pathway have?
Affect bronchial muscle, platelet aggregation and vasodilatation
clinical manifestations of allergy
trouble breathing
itching
sneezing
runny nose
headache
red or watery eyes
hives or rash
What are the conditions that elicit a type I hypersensitivity reaction?
Allergen characteristics
Host factors
Environmental influences
What makes certain proteins allergenic?
Allergens have the ability to induce a strong IgE response
Protease activity – Der p 1
Surface features of protein – Ves v 5
Glycosylation pattern of protein – Ara h 1
The clinical manifestations
Allergic rhinitis
Allergic conjunctivitis Atopic dermatitis
Urticaria/angioedema Asthma
Food allergy
Drug allergy
Venom allergy
Anaphylaxis
Treatment options
Anaphylaxis is a medical emergency Treatment consists of:
Adrenaline / epinephrine
Antihistamines
Corticosteroids
Fluid resuscitation
Bronchodilation
Other treatment options include: Allergen avoidance
Topical corticosteroids
Antihistamines
what is Desensitisation or allergen-specific immunotherapy?
A process whereby the immune system is exposed to gradually increasing doses of allergen in order to develop tolerance
how is Desensitisation or allergen-specific immunotherapy administered?
via subcutaneous or sublingual route
when is Desensitisation or allergen-specific immunotherapy used?
Used in allergic rhinitis, venom allergy and drug allergies predominantly
describe asthma
Partially a type I hypersensitivity phenomenon but also has type IV (cell mediated) and type V (tissue driven) mechanisms
Large proportion of asthmatics have T2-hi inflammation
Numerous monoclonal antibodies available
