1. Diseases Hypersensitivity- Types
Active sensitization in guinea pigs is induced by a single injection of a foreign protein such as egg albumin. After an incubation period of about 2 weeks, the animal is usually challenged with IV Inj of the same protein.
Within 1 min, the animal becomes restless, its respiration becomes labored, and its blood pressure drops. As the smooth muscles of the gastrointestinal tract and bladder contract, the guinea pig defecates and urinates. Finally bronchiole constriction results in death by asphyxiation within 2–4 min of the injection.
All S/S from vasodilation and smooth-muscle contraction brought on by mediators .
Postmortem:- massive edema, shock, & bronchiole constriction are the major causes of death.
Systemic anaphylaxis in humans is characterized by a similar sequence of events.

2. Types of Type 1 hypersensitivity
Type I Reactions Can Be
Systemic
Localized

3. SYSTEMIC ANAPHYLAXIS
occurs within minutes after the allergen is introduced in blood (bee sting or through gut)
Symptoms range from mild urticaria (hives) to shock-like symptom i.e.
anaphylaxis may become fatal e.g.
respiration may become labored
blood pressure may drop
Airway constriction
Swelling of epigottis
Difficulty in breathing
Usually against foods such as peanuts or bee sting

5. Some historians claim that Egypt's first pharaoh, Menes, was killed by a wasp's sting

6. Treatment
Epinephrine is the drug of choice for systemic anaphylactic reactions:
relaxing the smooth muscles and reducing vascular permeability
improves cardiac output

7. SYSTEMIC ANAPHYLAXIS Urticaria may be: Might be caused by:
Acute (type I)
chronic (type II)
Might be caused by:
venom from bee, wasp, hornet, and ant stings;
drugs, such as penicillin, insulin, and antitoxins;
seafood and nuts
If not treated quickly, these reactions can be fatal

8. Interestingly
Some IgE mediated anaphylaxis in response to insect venom, drugs or foods are not associated with atopy

9. LOCALIZED ANAPHYLAXIS (ATOPY)
Tendency to manifest localized anaphylactic reactions is inherited and is called atopy
In localized anaphylaxis, the reaction is limited to a specific target tissue or organ- epithelial surfaces at the site of allergen entry
Atopic allergies, which afflict at least 20% of the population in developed countries
include a wide range of IgE-mediated disorders
including allergic rhinitis (hay fever),
asthma,
Atopic dermatitis (eczema)
and food allergies

10. Late-Phase Reactions Induce Localized Inflammatory Reactions
As a type I hypersensitive reaction begins to subside, mediators released during the course of the reaction often induce localized inflammation called the late-phase reaction
The late-phase reaction begins to develop 4–6 h after the initial type I reaction and persists for 1–2 days
The reaction is characterized by infiltration of neutrophils, eosinophils, macrophages, lymphocytes, and basophils
The localized late-phase response also may be mediated partly by cytokines released from mast cells

11. Mediators of early and late phase responses of Type 1 hypersensitivity

13. Allergy- Treatments

14. Type I Hypersensitivities Can Be Controlled Medically
Avoid contact . Removal of house pets, dust-control measures, or avoidance of offending foods . Elimination of inhalant allergens –pollens is a physical impossibility
Type I Hypersensitivities Can Be Controlled Medically
to avoid contact with known allergens
Often the removal of house pets,
dust-control measures,
or avoidance of offending foods can eliminate a type I response

15. Immunotherapy the use of humanized monoclonal anti-IgE
repeated injections of increasing doses of allergens (hyposensitization) has been known for some time to reduce the severity of type I reactions
shift toward IgG production
to induce T-cell– mediated suppression