Download The Immune System and Allergy

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
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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
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
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Antihistamine
Decongestants
Inhalers
EpiPen
New epinephrine injectors
• Auvi - Q
Allergen Immunotherapy
• SCIT – subcutaneous (shot)
• SLIT – sublingual (drops under tongue)
Questions