Chapt. 4: Indoor and Outdoor Allergens and Pollutants Flashcards
What is the primary composition of allergens in and outside the home?
Proteins
Major route of exposure both inside and outside the home
Inhalation
Submicronic particles are more likely to be associated with rhinitis or asthma?
Asthma
The main source of outdoor allergen exposure?
Pollens and fungi
Most significant allergen sources in the home?
Mites, cockroaches, pets such as dogs and cats
Atopic dermatitis and anaphylaxis are associated with what food allergen sources?
Peanuts, milk and fish
Rhinitis and asthma are associated with what aeroallergens?
pollens and house dust mites
Meaning of allergen?
describes any of those that are capable of stimulating the production of specific IgE in a genetically predisposed individual
Most clinically significant route of exposure to allergens?
Respiratory tract
Meaning of allergenic?
describes the IgE-inducing property of an allergen
The terms allergen, allergenic, and allergenicity are synonymous with what terms?
antigen, antigenic, and antigenicity
Meaning of cross-reactive allergen?
because of a significant sequence homology (common epitopes), a patient will produce an IgE response to a primary allergen and also react to a related one.
What are some cross-reactive allergens?
tropomyosins in mites, snails, cockroaches, shellfish
In pollens and distantly related fruits what are the common allergens?
profilins
What is the OAS (oral allergy syndrome)/PFS (pollen food syndrome)?
Patients who are sensitized to pollen via inhalation and react to distantly related fruits.
What are the most complex glycoprotein mixtures allergens?
pollens, fungal spores, seeds and mites
What are the least complex glycoprotein mixtures allergens?
animal danders, urine and from occupational sources
What is the percentage of polysensitization?
70%. Monosensitization often precedes polysensitization.
Meaning of “major” allergen?
Allergens in a particular source that are recognized by >50% or more of allergic individuals. The remaining ones are “minor”.
What is important to the aerosolized particles, the aerodynamic or the absolute size?
The aerodynamic size.
What size particles will give rise to nasal symptoms as opposed to asthma?
> 10 um. Submicronic particles enter the bronchi and give rise to lower airways inflammation, resulting in asthma
Size will also affect what property of the allergen?
The length of time the particles are suspended in the atmosphere, and thus the exposure
How to express pollen and fungal spores?
Number of grains/spores/m3 per 24hours or pollen index of developing symptoms using the terms “low” “moderate” “high” “very high” and “extreme”
What are haptens?
LMW chemically reactive compounds which are allergenic
What are the most common haptenic compounds in clinical practice?
The beta lactam antibiotics such as the benzyl penicillins.
Every protein allergen contains a number of potential epitopes, which are also known as antigenic determinants. what are these?
These represent linear amino acid sequences or adjacent sections of a sequence that engage with either the B cell receptor or its soluble antibody form or the T cell receptor sitting on the surface of a lymphocyte.
What is the number of amino acid residues comprising a B cell epitope that interacts with the actual binding site of a B cell receptor or allergen-specific IgE?
5 amino acid residues
Are lipids allergenic?
Do not appear to be, although the lipid content of some sources such as pollens may play an adjuvant role in sensitization.
The therapeutic murine monoclonal antibody Cetuximab may cause delayed anaphylaxis (3-6hours) in some patients after ingesting what?
Red meat.
What is the proportion of individuals that are exposed who become sensitized to pollens and fungal spores?
30-40%
How does the age of the pollen influence manifestations?
Immature and aging pollens are not as potent as mature pollens.
Range of size of pollens?
5um - >200um
What is the structure of pollen?
Cytoplasmic core, a multilayered, tough, sporopollenin-containing external wall layer (exine), with various apertures and an internal wall, the intine
What is the exine structure in pollen?
Comprises three layers and provides the pollen with strong, mechanical resistance, enabling it to survive for long periods in the atmosphere.
What is the single most important allergen source associated with asthma?
HDM
Up to what percentage of asymptomatic individuals are sensitized to an indoor allergen?
15%
What is the optimum growth temperature for mites?
18-27 degrees
What is the atmospheric moisture requirement for HDM?
65-85% RH. (Absorbed through their joint legs or produced through metabolism because they are unable to drink).
What are the allergenic components of cockroaches?
Associated with their feces, saliva, and debris of dead insects
Cockroach allergen levels in bedrooms may correlate with the frequency of hospitalization, true or false?
True
What are some cockroach allergens?
aspartate protease, lipocalin, GUT-1 associated group 1 allergens, digestive enzymes (amylase, trypsin), arginine kinase, actin-associated proteins.
What are the 2 major sources of mammalian allergens?
Those containing lipocalcins (comprising >50% of all furry animal allergens) and the secretoglobins. (There is still a third minor group containing a small diversity of other proteins).
Why can cat-allergic patients report symptoms on entering a house in which a cat is living?
Because 10-40% of cat allergens are carried on particles that are aerodynamically equivalent to 1-7um spheres that sediment only slowly, such that free undisturbed air concentrations of cat allergen may be 10-50x higher than that of HDM.
What is the rate of air change/hour in modern housing?
0.2-0.5
Inhalational exposure to cat or dog allergen in houses with these pets?
100-fold (1ug/day) greater in homes with pets
Living in a house with a cat is selectively protective against developing a cat allergy. True or false?
True
Dogs have a generally inhibitory effect for allergy. T/F?
True
What are the predominant allergens in cat and rabbit dander?
secretoglobins. They may be immunomodulators because of their ability to bind lipid and activate TLR.
What is the “pork-cat” syndrome?
Cross-reactivity with canine, porcine, and bovine albumins.
What are the major allergens in dogs?
Lipocalcins (belonging to the calycine superfamily). They are produced in the liver or secretory glands and members of this family play a role in the binding and transport of small hydrophobic molecules such as vitamins and steroids.
What are other dog allergens?
Serum albumin, immunoglobulins and kallikrein
What is the prevalence of rat allergy in laboratory animal workers?
40%, with most becoming sensitized within 3 years of exposure (60%), and the remainder becoming sensitized within 5-20 years.
How long does it take from removing a cat from the home for allergen level to decrease?
12-16 weeks after cat is removed. It will take >4 months for levels of cat allergens to fall below 8 ug/g dust.
One of the most preventable risk factors contributing to the global burden of disease in allergy?
Air pollution
What are some indoor pollutants?
Biomass burning and tobacco smoke
What are the contaminants commonly responsible for poor air quality (both indoor and outdoor)?
Carbon monoxide, lead, sulphur dioxide, oxides of nitrogen, ozone, polyaromatic hydrocarbons, particulates, and miscellanous biologics such as LPS
Which of the contaminants do NOT directly affect airway tone or promote inflammation directly or indirectly?
Carbon monoxide and lead
What cellular mechanism is activated by these pollutants thus responses will be exaggerated in individuals with loss of function polymorphisms in antioxidant defense enzymes?
Oxidative stress
What are the main sources of indoor air pollution?
Biomass combustion (wood, crop, dung, grass and coal), nitrogen oxides, tobacco smoke and LPS
In indoor stoves lacking an effective flue, combustion is known to have a significant association with?
COPD and risk for lung cancer due to DNA damage
What is responsible for the adverse effects of biomass combustion?
Due to polyaromatic hydrocarbons that can be metabolized to oxidants, including quinones
How does ETS (Environmental tobacco smoke) contribute to the development of asthma?
Enhances allergen-induced IgE and IgG4 effects, and promotes a bias towards TH2 (IL-4, IL-5, IL-13 dependent) immune signaling at the expense of IFN-gamma production (i.e. TH1-mediated signaling)
What aerodynamic diameter of particulates will gain entry to the whole respiratory tract, therefore constituting a high health risk?
Diameter of 2.5 um. >2.5um will impact the larger airways, but not the alveoli
Toxic gas with a pungent, rotten odor whose contribution to acid aerosol formation means that it is extensively studied.
Sulfur dioxide
S/s of sulfur dioxide inhalation?
Shortness of breath, respiratory discomfort, and premature death. It increases the likelihood of developing asthma or COPD and is correlated with the presence of current symptoms.
What is the immediate effect of sulfur dioxide (<2mins.)?
Bronchospastic rather than inflammatory response, which involves wheezing, chest discomfort and dyspnea, but repeated exposure results in tachyphylaxis.
Is there a strong association between ambient NO2 concentrations and both acute and chronic changes in lung function and the exacerbation of asthma?
Yes.
What is the mechanism of NO2 on lung function?
Inflammatory neutrophilic infiltration.
This is a pungent pale blue gas and its strongly oxidant action is damaging to mucous and respiratory tissues and therefore has the potential to modify responses to inhaled allergens?
Ozone
How is ozone formed in the troposphere?
Formed by photochemical reaction between nitrogen oxides and volatile organic compounds from vehicle emissions and industrial discharges.
Is a well-recognized trigger for asthma exacerbations, even at low levels of exposure, and there is a significantly increased risk of death from respiratory causes at higher levels
Ozone
