Theme 2 Lecture 6: Allergic Diseases Flashcards
What is rhinitis commonly known as?
hay fever
What are the symptoms of rhinitis?
blocked/runny/itchy nose, sneezing
eye symptoms - itching, burning, watery eyes, redness
What is the treatment for rhinitis?
antihistamines or intranasal steroids
What type of hypersensitivity is allergic rhinitis?
type 1 - IgE mediated
What conditions are in the atopic triad?
rhinitis, asthma, eczema
What are the different types of rhinitis?
- allergic
- seasonal: pollen, moulds
- perennial: house dust mite, animal dander - non-allergic
- vasomotor
- infective
- structural
- drugs
- hormonal
- polyps
What is asthma?
disease of inflammation and hyper-reactivity of the small airway
In childhood, which pathogen is of pathogenic importance as an allergic stimuli?
house dust mite
Explain how an allergen presented to a patient can result in allergic asthma
- allergen presented to antigen presenting cell
- antigen interacts with Th2 cell to encourage proliferation
- Th2 cells secrete cytokines which cause B cells/plasma to secrete IgE antibodies
- mast cell, basophil and eosinophil secrete histamine, leukotriene etc
What are the symptoms of dermatitis/eczema?
intense itching, blistering/weeping, cracking of skin
Explain the process of sensitization and memory induction
- first, sensitization to allergens and development of specific B and T cell memory
- differentiation and clonal expansion of allergen-specific Th2 leads to production of cytokines
- Class switching to IgE
- IgE+ memory
- B cell clonal expansion
Explain the immediate phase of the allergic reaction
cross-linking and degranulation of mast-cell and basophil causes release of vasoactive amines, lipid mediators, chemokines, cytokines
-immediate symptoms of allergic disease
Give a summary of the late phase inflammation response
- allergen specific T cells are reactivated and clonally expand
- local IgE-facilitated antigen presentation by dendritic cells increases T cell activation
- Th1 cells produce IFN and TNF contribute to the activation and apoptosis of keratinocytes (in the skin), bronchial epithelial cells and pulmonary smooth-muscle cells
- activation of mast cells and basophils which release histamine
Explain the actions of T cells in allergic rhinitis and asthma
- Th2-cytokine-mediated induction of increased mucus production
- local production of IgE
- Th1-cell-mediated induction of bronchial epithelial-cell apoptosis
- eosinophils one of the main inflammatory cells
What are the actions of T cells in atopic dermatitis?
- Th1 cell mediated induction of keratinocyte apoptosis
- Th1 cell-mediated epithelial cell activation, and release of chemokines and pro-inflammatory cytokines
What does a specific IgE test measure?
the levels of different IgE antibodies
What are the methods of analysing raw allergen material?
- extraction –> extract immunoCAP
- recombinant technology –> component immunoCAP
- purification –> component immunoCAP
What are the two skin tests for allergies?
skin prick test and intra-dermal test
What size does the lesion in a skin prick test have to be for it to produce a positive result?
> 2mm wheal
What happens when there is crosslinking of membrane bound IgE and a basophil?
- basophils upregulate the expression of specific activation markers such as CD63, CD300a
- they become activated
What are the disadvantages to common allergy tests?
false positives and negatives
How does allergen specific immunotherapy work?
- decreases size of and number of cells in immediate phase and late phase allergic inflammation
- prevents the development of new allergic sensitizations and reduces progression of allergic rhinitis to asthma
- Th1:Th2 increases
- production of IL-10, TGF
- reduces number of mast cells and the ability of mast cells to release mediators
- improves quality of life of treated individuals
Name 6 major food allergens?
cows milk eggs legumes- peanut, soybean, tree nuts -fish -crustaceans/molluscs -cereal grains
What are the two ways a patient can experience food intolerance?
- food characteristics - pharmacologic, toxin
- host characteristics - metabolic e.g lactase deficiency, psychological
What are examples of IgE-mediated food allergies?
- anaphylaxis
- urticaria
- angioedema
- oral allergy syndrome
- acute rhinitis
- acute asthma
What are examples of non-IgE mediated food allergies?
- contact dermatitis
- dermatitis herpetiformis
- proctocolitis
- FPIES
- coeliac disease
- heiner’s syndrome
What are the clinical manifestations of allergic reactions?
- vomiting
- diarrhoea
- oral symptoms
- rhinitis
- bronchospasm
- urticaria
- angioedema
- anaphylaxis
Is atopic dermatis IgE mediated or not?
its both
What would you ask a patient who has recently had an allergic reaction?
- detailed description of reaction
- time between drug intake and onset of symptoms
- number of doses taken before onset
- aware of pharmacological effects and non-immunological ADR
How can you manage allergies?
- intradermal testing
- graded challenge
- desensitisation
What type of hypersensitivity causes anaphylaxis?
type 1
What type of hypersensitvity is caused by IgG antibodies?
type 2 and 3
How does IgE antibody cause allergic reaction?
mast cell activation
Which cells secerete IgE?
Plasma cells
What is the gold standard test for allergies?
graded challenge - exposing a patient to allergen in controlled environment
