Allergies Flashcards
Define Allergy
Exaggerated immune response to a non-microbial/environmental antigen
What antibodies are overproduced to cause Allergies?
Immunoglobulin E (IgE) antibodies
What are cytokines IL-4, 5 and 13 produced by?
Th2 cells, Mast cells and eosinophils
Define Atopy and name the type of disorders is it associated with?
Atopy is a genetically determined, exaggerated IgE-meditated immune response and is it’s associated with Type 1 hypersensitivity disorders such as asthma and hay fever.
What is Asthma? State it’s symptoms and cause.
Asthma is a chronic disorder of the airways with variable airflow limitation. Recurrent episodes of wheezing, breathlessness and cough.
Cause by inhaled allergens.
What is Rhinitis? State it’s symptoms.
It is a respiratory disease linked to asthma and it causes nasal congestion, itching and sneezing.
What is angioedema and urticaria? State the triggers.
Raised itchy, nettle rash such as hives and it is triggered by food and drug allergens such as ACEIs and NSAIDs.
Define Eczema.
It is a local inflammation of the skin that appears in early childhood induced by food such as egg and milk.
What is Anaphylaxis? State it’s triggers.
It is a sever allergic reaction which can be life threatening. It’s triggers are food, drugs such as antibiotics, latex and venom.
Systems involved - gastro, cardio, blood and respiratory
Describe Genetic Predisposition.
It is influenced by inheritance of several genes and chromosomes. The identification of susceptibility locus for Atopy on chromosome 5q, near the site of gene clusters encoding cytokines IL-4,5,9 and 13.
What is the Hygiene Hypothesis?
The cleaner the environment the less microbes.
Describe the Skin Prick Test.
Test selects allergens based on clinical history.
A drop of allergen on skin - small skin prick = skin reaction which results in local tissue swelling and degranulation.
What would diminish the sensitivity of the Skin Prick Test?
If the patient takes any antihistamines.
What are the controls in the Skin Prick Test?
histamine - positive
Saline - negative
What is Allergen Sensation? State the 2 events.
Exposure of allergen leading to an increase in IgE production.
- Differentiation of at T cells to Th2
- Stimulate B cells to switch to IgE production - Th2 cells produce cytokines and provide the CD40 ligand to lead antibody Class switching.
What are Mast Cells and Basophils?
They initiate an acute inflammatory response.
Basophils - reside in circulation
Mast Cells - function as immune sentinel cells and produce cytokines.
Where are Mast Cells found?
They are found in the connective tissue surrounding blood vessels and mucosal surfaces.
What are the granule contents of Mast Cells?
Histamine
Leukotrienes
Inflammatory cytokines
Neutrophils and eosinophils attracting cytokines
What is the granule content of Eosinophil?
T and B cell attracting chemokines
Fibrotic cytokines
Matrix metalloproteinases and collagenases
Describe the Early phase of an allergic response.
Physiological mechanisms and loss of organ function due to mucus production, vasodilation & swelling and bronchoconstriction.
Describe the Late phase of an allergic response.
Immunological mechanisms
Smooth muscle scarring
Recruitment of Immune cells into peripheral tissue
Describe the immediate phase of an allergic reaction.
Mast cell degranulation
Histamine release
