L08: Allergies [MCQ Set 2]

• Allergens come from sources like pollen, fungi, insects, domestic animals, and foods.

Allergen Sources and Reactions

• Grass pollen grains are a common cause of hay fever.
• A high IgE test result often indicates an allergy.
• IgE antibodies signal an allergic reaction.

Aerodynamic Properties of Allergens

• Grass pollen allergens are inhaled at approximately 10ng/day.
• Allergens are eluted from grains and become airborne when disturbed.
• Major inhaled allergens originate from sources that easily become airborne and contain molecules present in the air.
• Protein epitopes are the primary targets for IgE antibodies.

Allergens from Domestic Animals

• The cat allergen, Fel D1, comes from the species Felis domesticus.
• Fel D1 protein is continuously airborne.
• Inhalation of Fel D1 can reach 1ug/day, which is 100 times the quantity of mite/pollen allergens.
• Testing shows that 90% of individuals allergic to cats have an IgE antibody response to Fel D1.
• Allergy testing methods include skin prick tests and serum testing for IgE.
• Skin prick tests involve applying a small amount of cat allergen to the skin and then breaking the skin for entry.
• Symptoms of cat allergies, such as nasal, eye, and lung issues, can occur within 30 minutes of entering a house with a cat.
• Airborne allergen assays explain physical reactions; particles of cat allergens are smaller than mite particles or pollen grains.
• Cat allergens can float for extended periods with minimal air disturbance and easily transfer to public places via clothing.

Sensitization and IgE Production

• Immunization typically does not induce a persistent IgE response.
• IgE production can occur through different routes of antigen introduction.
• Early animal research indicated that low doses of antigens were the most effective at triggering IgE production.
• Later research using CFA-antigens and emulsion agents resulted in more IgG antibody responses, with IgE antibodies produced in germinal centers.

Allergic Specific Reactions and Symptoms

• Common allergy symptoms include trouble breathing, itching, sneezing, headache, red/watery eyes, hives, or rash.

Grass Pollen

• The properties of airborne pollen are suited to its role, with pollen releasing in windy, dry conditions to be carried by wind.
• When pollen contacts a wet surface, it releases proteins, causing a human IgE response.
• The main grass-related allergen is Lol p1.
• Pollen allergens trigger IgA and IgG antibody responses.
• IgA provides mucosal immunity and neutralization, found in saliva, tears, and mucous.
• IgG supports opsonization, neutralization, complement activation, and antibody-dependent cellular cytotoxicity.

Dust Mites

• The primary dust mite allergen, Der P1, found in fecal particles, contains a wide range of substances.
• These substances activate pathways that trigger innate immune responses, including TLR4 and TLR9.
• Toll-like receptor activation leads to the production of pro-inflammatory cytokines and inflammation.

Cat Dander

• The main cat dander allergen, Fel D1, targets IgE when inhaled.
• Active immunization of cats against Fel D1 involves vaccination with Fel-CuMV vaccines.
• Vaccination activates the immune system, causing B cells to secrete anti-Fel D1 antibodies.
• Anti-Fel D1 IgG circulates in the cat's body and binds to the allergen Fel D1, reducing its reactivity in cat secretions.

Anaphylaxis

• Anaphylaxis is a severe, life-threatening allergic reaction that occurs within seconds or minutes of exposure.
• It results from the immune release of histamine, neutral proteases (tryptase and chymase), and proteoglycans like heparin.
• Symptoms of anaphylaxis include a drop in blood pressure, airway narrowing, rapid weak pulse, skin rash, nausea, and vomiting, potentially leading to shock.
• Treatment for anaphylaxis includes an epinephrine injection, followed by emergency medical care.

Allergen Exposure Routes

• The transdermal route occurs when proteins applied to the skin induce inflammation.
• Allergens on the skin can cause local infiltration of eosinophils and basophils.
• Eczema, characterized by high skin permeability, is associated with high levels of IgE antibodies.
• Stinging insect allergies: different insects elicit different responses.
• Bee venom typically causes a systemic response.
• Fire ant stings result in an intense local skin reaction, leading to sensitization and IgE antibody production.
• Sublingual route, exposure induce tolerance, eating wide range of foods, 95% of population no allergic reaction .
• Oral route: exposure can induce tolerance; most of the population does not have allergic reactions to a wide range of foods.
• Certain foods with different proteins, such as ovalbumin, can induce sensitization and IgE antibody production.

Immune Deviation

• Experiment results show oral exposure to certain chemicals can induce prolonged tolerance to exposure via the transdermal route in mice.

Explore common allergen sources like pollen, fungi, and domestic animals. Understand how IgE antibodies signal allergic reactions and the aerodynamic properties of allergens, including cat allergens and their impact on individuals with allergies. Learn about major inhaled allergens and protein epitopes.