The Immune System and Allergy William L. Houser, Jr., M.D.

Overview of Human Immunity

Innate Immunity Barrier defense Skin Mucous membranes Secretions Internal defenses Phagocytic cells Antimicrobial proteins Inflammatory response Natural Killer (NK) cells Complement

Adaptive (Acquired) Immunity Humoral response Antibodies In body fluids Cell-mediated response Lymphocytes (cells) In body cells

Acquired Immunity Antigen detection by B lymphocyte B cell receptors 2 heavy and 2 light chains Antigen binding site

Acquired Immunity Antigen detection by T lymphocyte T cell receptor Alpha chain and Beta chain Bind only to antigens presented to T cells by a host protein produced by genes from the MHC

B and T cell Interaction Antigen presenting cell (dendritic cells, macrophages, and B cells) interact with T helper cell Activated T cell binds to B cell Activated B cells become plasma or memory B cells Secreted antibody from plasma cells

Antibodies Differ from B cell receptors only in the constant (C) region of the heavy chain The five major types of heavy chain constant regions determine the five major classes of antibodies (M, G, A, E, and D) Changes in the heavy chain gene that switch B cells from producing one antibody class to another occur only in response to antigen stimulation and specific regulatory signals from T cells (cytokines cause isotype switching)

Allergy An exaggerated immune response to certain antigens (allergens) Overproduction of IgE antibody specific to the allergen IgE binds to mast cells in the connective tissue of certain organs like the skin, nose, eyes, and lung. Recontact with the allergen binds the IgE on the mast cell and cause cells to degranulate releasing histamine and other mediators

Example of an Allergic Response

Why do people become allergic?

Contact with Allergens

Conditions caused by Allergy Anaphylaxis – whole body, more than 1 organ system, life threatening Caused by bee venom, foods including peanuts, tree nuts, and seafood, and medications Treated with epinephrine (EpiPen)

Conditions caused by Allergy Allergic rhinitis (nose) – sneezing, runny nose, stuffiness, itching Allergic conjunctivitis (eye) – watery, red, itching Perennial – dust mite, mold, animal dander Seasonal – mold, pollen (tree, grass, weed)

Conditions caused by Allergy Asthma – an inflammatory condition of the lung caused by allergy 60-85% of the time Cough, wheezing, shortness of breath Triggers – see below

Other Allergy Conditions Food allergy – can cause skin (eczema or hives), gastrointestinal, or systemic symptoms (anaphylaxis)

Other Allergy Condtions Bee venom allergy Drug allergy Latex allergy Contact allergy – nickel Skin allergy – eczema or urticaria (hives)

Eczema

Urticaria (Hives)

Diagnosis of Allergy History – type of symptoms, timing and duration, family history, past history Physical examination Testing –Skin testing –RAST or ImmunoCap (blood)

Skin Testing

Allergy Treatment Allergen Avoidance Medication Allergen Immunotherapy (Allergy Shots)

Allergen Avoidance Dust mites – bedding encasings, furnace filters, air cleaners, remove feather/down, remove stuffed animals Animals – remove Mold – clean, reduce humidity

Medication Antihistamine Decongestants Inhalers EpiPen

New epinephrine injectors Auvi - Q

Allergen Immunotherapy SCIT – subcutaneous (shot) SLIT – sublingual (drops under tongue)

Questions