Chapter 23 Allergic Conditions

1. Chapter 23 Allergic Conditions Renqian Zhong

2. Content TYPES OF IMMUNOPATHOLOGICAL HYPERSENSITIVITY DEFINITION OF ALLERGY DISEASE STATES METHODOLOGIES

3. TYPES OF IMMUNOPATHOLOGICAL HYPERSENSITIVITY

4. TYPES OF IMMUNOPATHOLOGICAL HYPERSENSITIVITY

5. DEFINITION OF ALLERGY

6. DEFINITION OF ALLERGY Clinicians usually reserve the term allergy to apply to acquired hypersensitivities that have an immune basis. Allergy usually is reserved for conditions mediated by immunoglobulin E (IgE) and lymphocytes.

7. DISEASE STATES

8. Rhinitis （Allergic Rhinitis）

9. Rhinitis Allergic rhinitis is one of the most prevalent disease states in western civilization. Approximately 15% to 20% of the general population is allergic as defined by positive skin tests to inhaled aeroallergen(s) and clinical symptomatology that results from exposure to them.

10. Asthma

11. Asthma Asthma may be defined as a condition of reversible obstructive airways disease in which there is a high degree of airway hyperirritability to agents such as methacholine and histamine. Asthma is best diagnosed by performing spirometry and determining the patient's reversibility with inhaled bronchodilators.

12. Allergic Asthma It was estimated that approximately 20% to 25% of all asthmatics had an allergic component to their disease. Allergy is a common feature of the childhood asthmatic, and the severity of childhood asthma is proportional to the number of positive skin tests and the severity of the reaction to those skin tests.

13. Occupational Asthma Occupational asthma also can occur in response to low-molecular-weight chemicals on an allergic or a nonallergic basis. Isocyanate sensitivity can be disabling and can result in asthmatic symptoms recurring hours after the initial exposure.

14. Urticaria and Angioedema

15. Idiopathic Urticaria and Angioedema It is possible that urticaria can be associated with an IgE-mediated response, as in the case of some forms of food and insect sting hypersensitivity. Most cases of angioedema are from mast-cell degranulation occurring in deeper dermal tissues.

16. Hereditary Angioedema Hereditary angioedema (HAE) is a rare condition resulting from the functional absence of the C1 esterase inhibitor molecule. The clinical state presents with recurrent orofacial and peripheral angioedema or with acute abdominal crises of pain and diarrhea.

17. Insect Venom Hypersensitivity

18. Insect Venom Hypersensitivity Hymenoptera venoms from bees, wasps, and ants are capable of stimulating the production of specific IgE. Reexposure to these venoms can initiate an IgE-mediated response that can result in allergic symptoms including generalized urticaria, oropharyngeal angioedema, asthma, and anaphylactic shock.

19. Adverse Reactions to Foods and Food Additives

20. Adverse Reactions to Foods and Food Additives The most common manifestations of IgE-mediated hypersensitivity to food proteins are nausea, vomiting, diarrhea, and urticaria and angioedema occurring within minutes after ingestion. Food hypersensitivity has been implicated in the pathogenesis of some cases of atopic dermatitis.

21. Atopic Dermatitis

22. Atopic Dermatitis Atopic dermatitis is a rather common disorder occurring in up to 4% of the population. It is associated with an eczematous dermatitis that can at times be generalized but tends to concentrate in the flexures of the neck and inguinal regions and in the popliteal and antecubital fossae.

23. Allergic Contact Dermatitis

24. Allergic Contact Dermatitis Contact dermatitis refers to any dermatologic condition that is triggered by contact with a substance. Allergic contact dermatitis is from a hypersensitivity triggered by a lymphocyte recognizing the offending material as foreign (a type IV response).

25. Drug Hypersensitivity

26. Drug Hypersensitivity Drug hypersensitivities may or may not have an immune etiology. Certainly, the most common cause of drug hypersensitivity is the IgE-mediated hypersensitivity to penicillin and its semisynthetic derivatives such as ampicillin and dicloxacillin.

27. Hypersensitivity Pneumonitis Hypersensitivity pneumonitis refers to a group of lung disorders having an immune etiology that are often caused by the occupational exposure to a sensitizing protein. Farmer's lung is a disorder triggered by the inhalation of spores of Micropolyspora faeni or thermophilic actinomycetes.

28. METHODOLOGIES

29. IgE-mediated Disease

30. Skin Testing Skin testing should be performed by personnel trained in its application with supervision by physicians experienced in the diagnosis of IgE-mediated diseases. In persons suspected of having IgE-mediated hypersensitivity to inhalants or foods, the percutaneous or epicutaneous skin tests should be applied first.

31. The most commonly used methods to determine total serum IgE include solid-phase immunoassay with fluorescence detection, radiolabeled immunoprecipitation, immunoplate enzyme-linked immunosorbent assay (ELISA), microparticle-enhanced immunoassay, and solid-phase immunoassay with luminescence detection. Total Serum IgE

32. Specific IgE The radioallergosorbent test (RAST) is the classic method for determining specific IgE antibody. This method generally has been replaced by the Immuno-CAP procedure, which uses an expanded cellulose matrix with high ligand binding capacity and enzyme based fluorescence detection.

33. Other in vitro Methods Other methods have been developed to quantitate specific IgE in vitro. In vitro methods with multiple allergens coupled to the support are available and can be used for screening for atopy. These methods are slightly less sensitive than using individual allergen tests, but can be used in a cost effective manner.

34. Clinical States Where Skin Testing, Specific IgE Antibody and Total IgE Are Useful The greatest utility for skin testing and specific IgE antibody lies in their ability to aid in the diagnosis of aeroallergen hypersensitivity and the resulting conditions of allergic rhinitis and asthma.

35. Cell-mediated Immunity (CMI)

36. Patch Testing Patch testing is the preferred method for diagnosing allergic contact dermatitis that is a result of a type IV hypersensitivity response. Performance of this testing requires an experienced investigator.

37. In Vitro Cytokine Production-1 Various lymphokines, cytokines, and interleukins (IL) can be measured in supernatants by enzyme-linked immunoassay using commercially available kits. Interferon-gamma and migration inhibition factor are correlates of cell-mediated immunity. IL-4 production is a correlate of IgE production.

38. In Vitro Cytokine Production-2 Production of IL-2, interferon-gamma, and tumor necrosis factor is typical of Th1 responses. Production of IL-4 and IL-13 are typical of Th2 responses. IL-5 induces maturation of and is chemotactic for eosinophils.

39. Thanks!