Week 2 Flashcards
Atopy is currently defined as?
Predisposition to produce IgE antibodies in response to the ordinary exposure to allergens in the environment
Who coined the term “allergy” to describe the phenomenon he had observed in which some patients, under certain conditions, developed an increased reactivity instead of immunity?
Austrian paediatrician, Clemens von Pirquet
Who proposed the term ‘atopy’ for the clinical manifestations of allergy such as hayfever and asthma in which ‘the individuals possess a peculiar capacity to become sensitive to certain proteins to which their environment and habits of life frequently expose them”.
In 1923, Coca and Cooke
Explain what is “reagin” when Prausnitz showed this in 1921
Prausnitz showed that atopic allergic sensitivity can be passively transferred from one individual to another by a serum factor
In 1967, what was the reagin known/named as?
Immunoglobulin E
Classically, allergic reactions are divided into four main types:
Gell and Coombs Types 1-4
Immediate or early reaction is defined when symptoms occur?
Occur within minutes of an immune reaction
Late reaction is when symptoms?
Start after hours
Delayed reaction is when symptoms are?
After days
Type 1 immediate reaction is caused by?
IgE and possibly IgG
Antigens which cause Type 1 reactions are called?
allergens
When the allergen reacts with IgE attached to the surface of the mast cell, what happens?
Mast cell degranulates and releases chemical mediators (histamine, SRS-A, ECF, PAF) responsible for the symptoms
Type 1 reactions depend on the presence of?
Specific IgE on high affinity receptors on mast cells.
There are also IgE receptors of both low and high affinity on other cell types, including?
Eosinophils and macrophages
Activated B cells (plasma cells) produce?
IgE
Activated B cells producing IgE which depends on exposure to the allergen and costimulation signalling via?
Activated T cells, which direct the B cell to the production of IgE
IgE synthesis results from?
Collaboration between a subset of T helper (Th) cells which produce IL-4, but not IFN-gamma (Th2 cells).
Th2 cells because of their ability to produce?
IL-5 and IL-4
IL-5 and IL-4 are responsible for the _____ which are often associated with?
Eosinophils; hyperproduction of IgE in allergic subjects
T-helper cells which do not produce IL-4 or which produce high concentrations of IFN-gamma do not support?
Do not support IgE synthesis
IFN-gamma can suppress?
Can suppress IL-4 dependent IgE synthesis
Regulatory T cells such as ___, ___ and ____ may also play a role in determining whether the response to ubiquitous environmental allergens is that of tolerance or of sensitisation and clinical allergy.
nTreg, Th3, and Tr1
Dysregulation of regulatory T cells (nTreg, Th3 and Tr1) is now thought to play a significant role in?
Development of the atopy
Promotion of a prevalent Th2 type response to environmental allergens (such as __, ____, ____, ____ etc) in atopic subjects almost certainly involves a genetic predisposition as well as environmental influences.
Foods, HDM, animal dander, pollen
What are wheezes?
Wheezes are continuous sounds generated from within the lungs during breathing
Wheezing sounds are superimposed on?
On normal breath sounds
Wheezes are sounds superimposed on normal breath sounds and are often referred to as?
Adventitial sounds
Wheezes may be characterised by their?
Pitch, intensity, location, duration in the respiratory cycle (short or long) and relationship to the phase of respiration in which they are heard (inspiratory or expiratory)
‘Continuous’ in the context of wheezes is in relationship to the phase of?
Breathing cycle, in which the sound occurs, i.e. the sound is continuous over 0.25 to 1.5 seconds of breathing
Crackles are?
They are a series of discontinuous ‘popping’ sounds
Analysing wheezing sounds using signal processing and analysis techniques has shown the dominant frequency of wheezing to be approximately?
400 Hz
Structure of the normal bronchial tree consists of a series of branches or generations from ?
- Trachea (generation 0)
- Through the left and right main bronchi (generation 1)
- Lobar bronchi
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs (with an average of 20 to 23 divisions or generations along the way)
While the calibre of each individual airway decreases with each division, total cross sectional area of the airways?
Increases with each generation
Linear velocity of airflow in very peripheral airways is?
Very low - far too low to produce an audible sound at this level, even with considerable airway narrowing.
Wheezing is produced by diseases or disease processes which?
Which directly or indirectly reduce the calibre or cross-sectional area of the trachea or major bronchi
While localised obstruction of the large airways can occur, dynamic narrowing of the trachea or major bronchi may also come about during expiration because of?
Widespread obstruction of the medium and smaller airways
The physiological explanation for narrowing of trachea/bronchi is referred to as?
Equal pressure point theory
Key elements involved in equal pressure point theory include:
Pleural pressure or pressure outside the airways (Ppl) which is usually negative during relaxed expiration, tending to keep the lungs inflated, and the elastic recoil pressure of the lung tissue (Pst[L]) which tends to empty the lungs.
Tissue forces driving relaxed expiration are the sum of?
Two values: pleural pressure (usually negative during relaxed expiration, keeps lungs inflated) & elastic recoil pressure of the lung tissue (tends to empty the lungs).
If airflow resistance increases, driving forces of relaxed expiration may be insufficient to produce airflow and must be an active process. So what happens?
Pleural pressure becomes positive during expiration and the pressure within the alveoli increases.
Pressure within the alveoli progressively falls along the airways to reach a pressure of zero at?
At the mouth, referred to as ‘downstream’ pressure
Downstream from the point where the pleural pressure exceeds the intraluminal pressure, what occurs?
Dynamic compression of the airways can occur
How is the wheeze is produced?
Because of the dynamic narrowing of these larger airways
High-pitched sounds of wheezing are produced when?
when the airway lumen is narrowed to the point where the opposite walls are almost in contact
Mechanisms underlying the production of a wheezing sound with breathing seem to involve an interaction between?
Airway wall and gas moving through the airway
Acceleration of gas flow through the narrowed airway induces?
Induces an oscillation of the airway walls.
Pitch of the wheeze depends upon?
Depends upon the mass and elasticity of the airway walls and on the flow velocity of the gas within the airway.
Pitch of the wheeze is not influenced by?
Influenced by the length or size of the airway
Inspiratory wheezes are explained by?
Actually, no theory has yet to be proposed.
During inspiration, airways are held open by?
Elastic tissues of the lung
In some circumstances, when airways are not sufficient to enlarge an airway, what happens?
Flow limitation with airway wall fluttering occurs
Inspiratory wheezes are often associated with?
With more severe airways obstruction or upper airways obstruction