Diseases Hypersensitivity- Typ
DiseasesHypersensitivity- Types
Types of Type 1 hypersensitivity
• Type I Reactions Can Be – Systemic – Localized
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
Some historians claim that Egypt's first pharaoh, Menes, was killed by a wasp's sting
Treatment
• Epinephrine is the drug of choice for systemic anaphylactic reactions:– relaxing the smooth muscles and reducing
vascular permeability– improves cardiac output
SYSTEMIC ANAPHYLAXIS
• Urticaria may be:– 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
Interestingly Some IgE mediated anaphylaxis in response
to insect venom, drugs or foods are not associated with atopy
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
Late-Phase Reactions Induce LocalizedInflammatory 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
Mediators of early and late phase responses of Type 1 hypersensitivity
Allergy- Treatments
Type I Hypersensitivities Can BeControlled 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
Avoid contact . Removal of house pets, dust-control measures, or avoidance of offending foods . Elimination of inhalant allergens –pollens is a physical impossibility
Immunotherapy• 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
• the use of humanized monoclonal anti-IgE