*Allergy Flashcards
1
Q
ALLERGY PATHOPHYSIOLOGY
A
- Allergies and autoimmune disease are hypersensitivity
reactions of an over-reactive immune system to exogenous
and endogenous antigens, respectively - Itch is a pathognomonic symptom of allergy
- Histamine is a principal mediator of itching
- Itch along with symptoms of dryness (burning, gritty, scratchy)
may be resolved with dry eye therapy - When present, clinical signs & symptoms of inflammation
(redness, warmth or heat, swelling, pain or notable discomfort)
may call for combination anti-inflammatory therapy
2
Q
HISTAMINE PHARMACOLOGY
A
- Histamine is expressed throughout the body by a large variety of
cells and neurons, in the latter case acting as a neurotransmitter - For allergies, histamine predominantly acts through the H1 receptor,
resulting in:- Vascular permeability
- Runny nose, watery eyes, swollen lids, papillae
- Vasodilation
- Redness, headache, hypotension, reflex tachycardia
- Smooth muscle contraction
- Bronchoconstriction
- Sensory nerve stimulation
- Pain & itching, sneezing, coughing
3
Q
EXOGENOUS AGONISTS OF THE IMMUNE RESPONSE
A
Apart from endogenous pathways, many foreign substances (antigens),
as well as physical processes, have the capacity to evoke an
immunological response
Physical Activators
• Temperature, pressure
Environmental Antigens
• Animal dander, ragweed, pollen, dust, insect bites, venoms
Biological Antigens
• Bacteria, viruses, fungi, parasites
Chemical Antigens
• Vaccines, drugs, proteins, carbohydrates, metals, food additives
4
Q
*ANTIHISTAMINE PHARMACOLOGY
A
- Classic antihistamines aka 1st generation antihistamines are highly lipophilic and therefore enter the CNS and other tissues readily
- 2nd generation antihistamines do not readily enter the CNS and therefore have less associated adverse FX
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5
Q
INNATE IMMUNE RESPONSE
A
A non-specific generic acute response
- A first-line defense lacking immunologic memory
- Acts near entry-points of infection or injury
- Humoral
- Activation of the non-classical (alternative) complement cascade in response to microbe surface interaction
- Release of cytokines by first-responder TH-2 cells
- Cell-mediated
- Phagocytes ingest foreign proteins, fungi, pathogens viruses, bacteria, and parasites and NK cells secrete cytokines to recruit monocytes (premature macrophages) and neutrophils
6
Q
ADAPTIVE IMMUNE RESPONSE
A
An acquired specific response
- Requires prior exposure to the antigen
- Evasion of the innate response may occur
- Features both specificity & memory
- Humoral
- Activation of the classical complement cascade in response to Ag-Ab complexes
- Exposed dendritic cells (APC’s) stimulate T cells to mature into Helper T’s which cause B-cells to transform into antibody-producing plasma cells
- Memory B-cells secrete antibodies upon re-exposure
- Cell-mediated
- Exposed dendritic cells (APC’s) stimulate T cells to mature into Helper T’s which facilitate sensitization of Killer T’s
7
Q
P12
A
8
Q
ANTIGENS
A
Foreign substances having the capacity to
evoke an immunological response
- Environmental Antigens
- Animal dander, Ragweed, Pollen, Dust, Insect stings
- Biological Antigens
- Bacteria, viruses, fungi, parasites
- Chemical Antigens
- Vaccines, drugs, proteins, carbohydrates, metals, food additives
9
Q
P14
A
10
Q
P15
A
11
Q
MAST CELLS
A
- The Type I Hypersensitivity Reaction employs mast cells as its
effector cells; wheal and flare are hallmark signs of degranulation - Mast cells, found throughout the body, play a key role in the
development and maintenance of allergic reactions, thereby rendering them as attractive therapeutic targets - Mast cells release mediators from 3 major sources:
- Preformed (seconds): histamine, proteases, serotonin, heparin
- De novo synthesis (minutes): eicosanoids (leukotrienes and
prostaglandins); products of the arachidonic acid cascade - Induced transcription (hours): gene expression of chemokines,
cytokines, TNF-a, growth factors
12
Q
P17
A
13
Q
ANAPHYLAXIS
A
An acute, systemic hypersensitivity reaction to a previously sensitized allergen
- Ige in the bloodstream reacts with the antigen leading to a robust release of chemical mediators resulting in impaired respiration (bronchoconstriction), dramatically reduced blood pressure (vasodilation), and swelling
- Monitor respiration
- Place patient in supine position to maximize blood flow to CNS
- Monitor blood pressure
- Avoid any oral hydration; smelling salts may be considered prn
- Serious anaphylactic reactions develop within minutes (up to 2 hours) and require immediate emergency treatment with epinephrine (epipen)
- O2, IV steroids, and airway management, including intubation, should also be considered as indicated; be prepared to call for medical support
14
Q
Cautions for use of epipens
A
Caution in patients with heart disease or high blood pressure,
Parkinson’s disease, diabetes, or a thyroid disorder
15
Q
TYPE IV DELAYED HYPERSENSITIVITY
A
- Re-exposure (memory) response
- E.g. TB testing, MS, chronic transplant rejection
- T-cell based unlike Types I-III; antibody independent
- NOT responsive to antihistamines
- Most responsive to steroid therapy
