Type IV hypersensitivity disease

Introduction to type IV hypersensitivity diseases It is believed that the clinical diseases in which type IV response plays an important role include contact dermatitis, hypersensitivity pneumonitis, allograft rejection, intragranular pathogen-induced granulomatosis, certain types of drug allergy, thyroiditis, and rabies vaccination. Occurrence of encephalomyelitis. The latter two conditions were confirmed in animal models. In human diseases, lymphocytes were confirmed based on the presence of lymphocytes in the inflammatory exudates of the thyroid and brain. basic knowledge The proportion of illness: 0.02% - 0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: pneumonia thyroiditis

Type IV hypersensitivity disease etiology

The body is destroyed by its own stabilizing effect and antibodies (or cells) mediated by its own tissue components, also known as autoimmune reactions, which occur for:

1 The emergence of a new antigen or the release of the original concealed antigen, the immune system is not tolerated, once contact (such as due to trauma caused by release), that is, an immune response, such as sperm that has not formed before puberty, viral infection or malignant transformation New antigen formed;

2 After some changes in the normal components of the body, the exposed new antigenic determinants stimulate the immune system to cause autoimmunity. For example, the antibody is deformed and twisted due to binding with the antigen, and some amino acid sequences that are not revealed before binding are exposed (can be used as Antigenic determinants, which stimulate the body to produce antibodies against its own components, as can some components of the complement system. Antibodies formed in this way can only react with determinants exposed by deformed antibodies or complements, rheumatoid The rheumatoid factor specific to arthritis is the corresponding antibody against the altered immunoglobulin; 3 due to the immune function of the cross-reactive antigen, it can also stimulate the body to produce an immune response against itself. These cross-reactive antigens may have some The same antigenic determinant. For example, after some strains of Streptococcus cause infection (rheumatoid fever), antibodies against the myocardium and endocardium may occur.

Type IV 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 IV hypersensitivity disease complications Complications pneumonia thyroiditis

Common complications of this disease:

1, dermatitis.

2. Pneumonia.

3. Allograft rejection.

4, granulomatosis.

5, thyroiditis.

6, encephalomyelitis.

Type IV hypersensitivity disease symptoms common symptoms erythematous rash blisters

When the inflammatory response is characterized by histological features of perivascular lymphocytes and macrophage infiltration, it can be suspected to be type IV. Delayed hypersensitivity skin test and patch test are the most stable and feasible methods for testing delayed type hypersensitivity. In order to prevent the increase of contact dermatitis, the patch test should be carried out after the dermatitis subsides. Apply suspicious allergen (appropriate concentration) to the skin, covered with a non-absorbed sticky patch, and left for 48 hours. When there is a burning sensation and itching, the patch is removed. The positive reaction is erythema and a certain degree of induration, and occasional blisters are formed. Because sometimes the reaction does not occur until the patch is removed, the local need is 72 hours and 96 Watch again in hours.

Examination of type IV hypersensitivity diseases

1, delayed hair hypersensitive skin test.

2, patch test.

Diagnosis and diagnosis of type IV hypersensitivity diseases

Diagnosis can be based on medical history, clinical symptoms, and laboratory tests.

Differential diagnosis

Type I hypersensitivity: also known as allergic allergy or immediate allergic reaction, because the antigen interacts with antibodies (usually IgE) on the medium-releasing cells, so that the Fo of IgE on the cells is bridged by fibers, causing cell activation. The membrane of the intracellular granule fuses with the membrane to form a conduit, which releases some active mediators such as histamine, serotonin, and slow-reacting substance-A (SPS-A). These mediators can cause smooth muscle contraction, telangiectasia, and transparency. Increased sex and increased glandular secretion, depending on the target cells affected by these active substances, respiratory allergic reactions, digestive tract allergic reactions, skin allergic reactions or anaphylactic shock, common type I hypersensitivity reactions with penicillin allergic reactions, drugs Caused by drug eruption, food-induced allergic gastroenteritis, allergic rhinitis caused by pollen or dust, bronchial asthma, etc.

Type II hypersensitivity reaction: also known as cytolysis allergy or cytotoxic allergy, 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 transfusion reaction The hemolytic reaction of the newborn and the hemolytic anemia caused by the drug belong to the type II hypersensitivity reaction.

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

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