Abnormal Immunity Continued: Allergies

Allergies Immune system response to a substance called an allergen (one that doesn’t actually present a threat) Allergen particles range in size and this helps to determine the reaction that ensues ex) Grass Pollen (LARGE) → remains in upper respiratory tract and triggers “hay fever” - runny nose/watery eyes ex) Cat dander (SMALL) → can infiltrate lungs and trigger asthma

Asthma Chronic disease in which contractions of the airways, inflammation, & accumulation of mucus all block airflow Rescue medications (inhalers) can loosen the muscles around the airways → open up the airways & make it easier to breathe

EpiPens They work by injecting a dose of the hormone epinephrine (adrenaline) into a person's body. Used during a severe allergic reaction Epinephrine constricts the blood vessels → reduces swelling in airways & increases blood pressure Start here genetics 2

Allergic Response Both B & T cells take part in an allergic response Antibodies (from B cells) bind to Mast Cells Antibodies release signals that open Mast Cells (cells found in connective tissue) → Mast cells release a substance called histamine

Allergy Mediators Histamine → Mediator compound that comes from Mast Cells Histamine- a vasodilator which promotes blood flow to tissues.

Allergy Mediators anaphylactic shock Cause inflammation with symptoms like runny eyes/nose (hay fever), narrowed airways (asthma), and rashes (dermatitis) An overwhelming, body-wide allergic reaction is called... anaphylactic shock

Mutations Misdirected immune response of an allergy can be caused by a mutation having half of the normal skin protein filaggrin can lead to development of allergic conditions like dermatitis (eczema), asthma, peanut allergy, & hay fever Start here genetics 1

Filaggrin Filaggrin is a large protein that binds to keratin (a fibrous protein forming the main structural constituent of hair) Together they help to form the epidermis, the outermost layer of skin → barrier against pathogens and allergens

Rare Genetic Disease Ichthyosis vulgaris- 2 mutations in the filaggrin gene that cause severe skin flaking About 1 in 10 of us have a mutation that causes this disease so mildly that we just treat it with skin lotion

Rare Genetic Disease Harlequin Ichthyosis vulgaris http://www.youtube.com/watch?v=OxIWUoJ-Dm0

Connections Cracked epidermis skin allows allergens to enter & reach deeper skin layers where they encounter dendritic cells Once activated, these cells signal inflammation → dermatitis Also activate immune memory so that years later when inhaling the same allergen that once crossed the skin, the immune response ensues in airways

Peanut Allergy Occurs when immune system mistakenly identifies peanut proteins as harmful Direct or indirect contact with peanuts causes your immune system to release symptom-causing chemicals into your bloodstream

Review Allergic Reaction 1) 1st exposure to allergen, antibodies from B cells attach to Mast cells 2) 2nd exposure to allergen → allergens combine with antibodies on mast cells 3) Mast cells burst and release histamines that cause the common itchy eyes and runny nose symptoms

Research Scientists are currently testing whether treating breaks in the skin earlier in life can prevent future dermatitis, asthma, and other allergies