Type I hypersensitivity disease

Introduction to type I hypersensitive reactive diseases Diseases associated with type I hypersensitivity reactions include atopic diseases: allergic rhinitis, allergic conjunctivitis, atopic dermatitis and allergic asthma, exogenous and some urticaria, gastrointestinal food reactions and systemic Allergic reactions, although the cause of asthma has not yet been elucidated, its incidence has increased significantly. In recent years, it has been noted that a significant increase in type I hypersensitivity reactions is associated with water-soluble proteins that are in contact with latex articles (eg, rubber gloves, dental trays, condoms, tubing for breathing apparatus, catheters, latex sleeves that are inflated at the tip of the enema), Particularly seen in health care workers and patients exposed to latex, as well as children with spina bifida and urogenital defects at birth, common reactions to latex are urticaria, angioedema, conjunctivitis, rhinitis, bronchospasm and anaphylactic shock. basic knowledge Probability ratio: 1.5% probability of population disease Susceptible people: no special people Mode of infection: non-infectious Complications: shock

Type I hypersensitivity disease etiology

There are many kinds of allergens, and there are 1 different kinds of proteins: such as heterogeneous animal serum, bee venom, insect venom, vaccine, parasite, food, pollen, insulin, etc.; 2 drugs: such as various antibiotics, organic iodine, amalgam Wait. Atopic diseases (including atopic dermatitis) have a genetic quality in which patients develop inhaled or ingested substances (allergens) with hypersensitivity mediated by IgE antibodies, and those who have no atopic disease It is harmless. In addition to atopic dermatitis, IgE antibodies usually mediate hypersensitivity reactions. In infants and young children, although the symptoms of dermatitis are caused by IgE-mediated food allergies, in older children and adults, dermatitis symptoms To a large extent, it has nothing to do with allergic factors, although most patients still maintain specific allergies.

Type I hypersensitivity disease prevention

Autoimmunity is a complex, multi-factor effect of natural phenomena, in addition to boundary effects (such as drug haptens, microbial infections), but also closely related to the body's own genetic factors, especially in the main tissue compatibility system. The immune response gene and/or the immunosuppressive gene are abnormal, so the most important aspect of prevention is to avoid contact with allergens.

Type I hypersensitivity disease complications Complications

The common complication of this disease is shock. This type of reaction has two types: local and systemic: local reactions often manifest as local tissue edema, eosinophil infiltration, increased mucus secretion or bronchial smooth muscle spasm, such as skin urticaria (food allergies), allergic rhinitis (Hard grass fever) and asthma. Systemic allergic reactions such as anti-serum, drugs (such as penicillin) anaphylactic shock, can cause rapid death. At the time of autopsy of death, laryngeal edema, edema of both lungs, sometimes accompanied by acute emphysema and right heart dilatation, blood does not coagulate, and the remaining viscera usually has no characteristic morphological changes except for congestion.

Type I hypersensitivity disease symptoms Common symptoms Itching epidermis keratosis eczema nasal mucosa pale edema apes herpes nausea dyspnea

(1) Hay fever, hay fever, also known as allergic rhinitis, is mainly caused by inhalation of plant pollen sensitization, so it has seasonal and regional characteristics. The clinical manifestations of the disease are mainly in the nose, eyes and respiratory tract. It can be seen that the nasal mucosa is pale and edematous, conjunctival hyperemia, etc. It is not difficult to diagnose according to the symptoms and skin test results of pollen infusion. Antihistamines can significantly control clinical symptoms, and can also be used in nasal and ocular local steroid and mast cell stabilizers. Drugs such as disodium cromoglycate can often receive good results in desensitization before pollen season.

(2) Bronchial asthma is a widespread and reversible airway stenosis disease caused by allergen or other factors caused by bronchial hyperresponsiveness. The incidence rate in Beijing is about 5%, which is an important respiratory disease in pediatrics and internal medicine. Occurs in children and young adults, has a clear family history, prolonged illness, long course of disease, frequency-sensitive episodes, more complications, the United States each year due to asthma death of about 2,000 to 3,000 cases, and there is an increasing trend, causing asthma is very Widely complex, inhalation and ingestive allergens, as well as infections, especially respiratory viral infections, are important causes of asthma. The main pathological changes are small bronchial smooth muscle contracture, telangiectasia, increased permeability, and small bronchial mucosal edema. Increased mucosal gland secretion, mucus plug formation, and thus narrow airway, patients feel chest tightness, difficulty breathing, these pathological changes and symptoms are mainly the result of LTs and histamine, bronchial asthma classification, differential diagnosis, prevention and treatment Although much progress has been made, there are still many problems to be resolved.

(3) Atopic dermatitis, also known as atopic dermatitis, is a common skin allergic disease. About 70% of patients have a positive family history. Most patients have elevated serum IgE levels. The lesions are mainly rash, characterized by intense itching. The pathological changes in the acute phase are interstitial edema and epithelial herpes formation. The superficial dermis may have edema, vasodilation and infiltration of lymphocytes and eosinophils. There are vesicles and keratinization in the subacute stage. A large number of lymphocytic infiltration; chronic atopic dermatitis mainly manifests keratinization and hyperplasia of the epidermis, thickening of the skin, lichenification, infiltration of a large number of inflammatory cells around the blood vessels, often pigmentation, rashes occur in the elbow fossa, armpits, neck Department and face, the disease can be divided into infant type, child type and adult type, infant atopic dermatitis is also called infant eczema, more than 4 to 6 months after birth, the lesions are exudative and dry type, adult The type is mostly in the onset of adolescence, which is characterized by generalized flattened papules, thickened skin and mossy lesions. Atopic dermatitis is sensitive to physicochemical and other stimulating abnormalities. Most patients have intermittent episodes and are prone to recurrence in winter. It should be based on the typical skin manifestations and a positive family history.

(4) Food allergies generally occur within a few minutes to 1 hour after eating. Symptoms include erythema, lip swelling, oral pain, glossopharyngeal, nausea, vomiting, etc. The common foods that cause allergies in young children are eggs, milk, Fish and nut nuts.

Examination of type I hypersensitivity diseases

Non-specific test eosinophils in blood and secretions are associated with atopic diseases, especially asthma and atopic dermatitis. In atopic dermatitis, IgE concentration is increased, and IgE concentration will increase when the disease is aggravated. Decreased. Although IgE is often elevated in atopic asthma and allergic rhinitis, it has no diagnostic significance for these diseases. Occasionally very high concentrations of IgE may be helpful in the diagnosis of pulmonary fungal disease or high IgE syndrome. .

Specificity tests can determine sensitivity to a particular allergen or multiple allergens. Skin tests are the most appropriate method for determining specific sensitivity. Skin test allergens should be selected as much as possible based on medical history. Clue. Test solution for extracts prepared by inhalation, ingestion or infusion of allergens (eg tree, garden and weed wind pollen, house dust mites; animal dander and serum; insect venom; food and penicillin and its derivatives Recently, a small number of allergen extracts have been standardized, and their potency is variable. Many commonly used extracts are now standardized.

First, a special prick test is used. When the test is done, a drop of diluted allergen extract is added to the skin, and then the skin is punctured or pierced. Usually, a thin probe tip or a 27-point tip is used to pick up the skin at an angle of 20°. Until the tip of the needle feels slack.

In the intradermal test , a diluted sterile extract is injected into the skin to produce a 1 or 2 mm blister (using a 1 ml syringe and a 27-gauge short bevel tip). Each skin test should include a separate dilution of the negative control and histamine (pricking) The test is a positive control of 10 mg/ml or an intradermal test of 0.1 mg/ml. If wheal and erythema are produced within 15 minutes, and the diameter of the wheal is at least 0.5 cm larger than the control, it is positive.

Skin prick tests are usually sensitive enough to most allergens. A more sensitive intradermal test is used when an inhaled allergen is suspected and the prick test is negative or ambiguous. For food allergies, the prick test can be used alone for diagnosis. Intradermal test A positive reaction may have occurred, but the challenge test with double-blind oral challenge symptoms confirmed no clinical significance.

Radioactive allergen adsorption test (RAST) is used in patients with systemic dermatitis, extreme skin scratches or patients who cannot cooperate or can not stop antihistamines, and direct skin tests are not possible. RAST detection of allergen-specific serum IgE, a known conjugate of an allergen into an insoluble poly-allergen, mixed with the serum to be tested, the allergen-specific IgE present in the serum will be adsorbed on the conjugate, followed by the addition of 125I-labeled anti-IgE antibody To measure the radioactivity of the conjugate, the specific IgE content in the patient's circulation can be determined.

The leukocyte histamine release test is an in vitro test to detect allergen-specific IgE on sensitized basophils by measuring the amount of histamine released by the patient's leukocytes under induction of allergens. This is a valuable research tool. The mechanism of allergic response can be understood. Similar to RAST, it provides non-diagnostic information and occasionally for clinical use.

The challenge test can be applied to a skin test positive, but when this particular allergen is associated with symptoms, the allergen is applied to the eyes, nose or lungs, and the eye challenge test is usually not superior to the skin test, so it is very Less use. The nasal stimulation test is accidentally used, mainly as a research method. The bronchial provocation test is mainly used as a research method. When the significance of a positive skin test is not clear or there is no suitable skin test agent, the substance in contact with the patient can be proved. The bronchial provocation test is sometimes used when the correlation is related to occupational asthma. When it is suspected that the regular symptoms are related to food, and the clinical significance of the skin test is unclear, it can be used as an oral challenge test. The reagent is a skin test. If it is negative, it cannot exclude the possibility that the clinical symptoms are caused by food. The challenge test is the only method that can detect allergies of food additives.

Test skin or sublingual challenge tests or leukocyte toxicity tests that have not been proven effective have no clear evidence that they can be used for the diagnosis of allergic diseases.

Diagnosis and identification of type I hypersensitivity diseases

diagnosis

Judgment can be made based on medical history, clinical performance and laboratory data.

Type I allergic reaction, also known as anaphylaxis, is called "immediate hypersensitivity" because of its rapid response. This type of allergy is caused by the antigen (sensitizer) entering the body and binding to IgE molecules attached to mast cells and basophils, and triggering the release of biologically active substances, causing smooth muscle contraction and increased vascular permeability. Clinical manifestations and pathological changes such as increased serum secretion.

Differential diagnosis

1. Type II hypersensitivity reaction: also known as cytolysis allergic reaction or cytotoxic allergic reaction. When the antigen on the cell binds to the antibody, the cell is destroyed due to the action of complement, phagocytic or K cell, such as blood type mismatch. The transfusion reaction, the hemolytic reaction of the newborn and the hemolytic anemia caused by the drug belong to the type II hypersensitivity reaction.

2, type III hypersensitivity reaction: also known as immune complex type allergy, which is caused by deposition of medium-sized soluble antigen-antibody complex into capillary wall or tissue, activation of complement or further recruitment of white blood cells, belonging to type III The disease is part of glomerulonephritis after streptococcal infection, exogenous asthma, etc., Arthus reaction is a local type III hypersensitivity reaction, after repeated injection of antigen (such as rabies vaccine, insulin), local An inflammatory reaction such as edema, hemorrhage, and necrosis occurs.

3. Type IV hypersensitivity, also known as delayed allergic reaction, is a pathological manifestation of cell-mediated immunity. It is mediated by T cells. The common type is: chemicals (such as dyes) bind to skin proteins. Or change its composition, become an antigen, can make T cells sensitized, after contact with the antigen again, T cells become killing cells or release lymphokines cause contact dermatitis, another type is called infectious allergic reaction, is caused by certain Pathogens are caused by antigenic stimuli and are found in tuberculosis, syphilis, etc. In addition, rejection of organ transplantation, encephalomyelitis after vaccination, and certain autoimmune diseases belong to this type.

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