Info

Fig. 13.3. Hypersensitivity Type I: sensitization phase, effector phase, and desensitization. Type 2 cytokines induce isotype switching to IgE. IgE binds to FceR present on mast cells or basophils. Re-exposure to antigen induces crosslinking of IgE, bound to mast cells and basophils and release of histamine and other inflammatory mediators. Local reactions induce allergic responses, while systemic reactions induce anaphylactic shock. Desensitization involves induction of isotype switching to IgG by B cells following antigen recognition in the presence of T cell derived Type 1 cytokines and appropriate costimulatory molecules. On subsequent exposure to antigen, circulating IgG binds the antigen before it binds to IgE present on mast cells and basophils.

Allergic rhinitis

Allergic rhinitis refers to inflammation of the nasal mucus membranes, sneezing, nasal congestion, and watery discharge from the eyes following antigen exposure.

Asthma

Asthma can be triggered by extrinsic antigens (immediate hypersensitivity), or by nonimmune mechanisms such as infection, exercise and cold air. Wheezing occurs when respiratory passages narrow (bronchoconstriction) following mediator release.

Anaphylaxis

Anaphylaxis is a systemic, potentially fatal, reaction that affects both the cardiovascular and respiratory systems, leading to cardiac arrhythmia, and hypotension.

Therapy

Treatments for patients susceptible to hypersensitivity reactions include (i) minimizing the exposure to the antigens that trigger the reaction, (ii) pharmacological intervention, and (iii) desensitization.

Pharmacological

Prophylactic pharmacological interventions include antihistamines or sodium cromoglycate. Anti-histamines are Hl-histamine receptor antagonists that competitively inhibit binding to Hl-binding sites. Sodium cromoglycate stabilizes the mast cell and basophil membranes, decreasing the release of inflammatory mediators following crosslinking of cell bound IgE by antigen. Epinephrine administration is NOT prophylactic but is an important antidote following exposure to agents triggering severe, life-threatening, immediate type hypersensitivity reactions (anaphylaxis). Epinephrine provides transient protection (for 30-90 minutes). Steroids are also administered, to control the persistent/recurrent symptoms over the four to eight hours postexposure (during which the inciting agent is generally cleared from the body). Individuals known to be at risk for anaphylaxis often carry injectable epinephrine.

How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book


Post a comment