What Are Hypersensitivity Reactions?
Hypersensitivity, that is, an abnormal, too high immune response. That is, the body interacts with antigenic substances under certain conditions to produce sensitized lymphocytes or specific antibodies. If combined with re-entered antigens, it can lead to immune pathological reactions in which the body's physiological functions are disturbed. Also called allergic reaction.
- nickname
- Hypersensitivity
- English name
- hypersensitivity
- Hypersensitivity, that is, an abnormal, too high immune response. That is, the body interacts with antigenic substances under certain conditions to produce sensitized lymphocytes or specific antibodies. If combined with re-entered antigens, it can lead to immune pathological reactions in which the body's physiological functions are disturbed. Also called allergic reaction.
Introduction to Hypersensitivity
- Hypersensitivity
- Abnormal, too high immune response. That is, the body interacts with antigenic substances under certain conditions to produce sensitized lymphocytes or specific antibodies. If combined with re-entered antigens, it can lead to pathological immune responses to physiological dysfunction and tissue damage of the body. Also called allergic reaction. Antigenic substances that cause hypersensitivity are called allergens. It can be a complete antigen (xenogeneic animal serum, tissue cells, microorganisms, parasites, plant pollen, veterinary fur, etc.), or a hapten (such as drugs such as penicillin, sulfa, phenacetin, or low molecular weight such as raw lacquer) substance). It can be exogenous or endogenous. The clinical manifestations of hypersensitivity reactions are diverse and can vary depending on the nature of the allergens, the pathways into the body, participation factors, mechanisms of occurrence, and differences in individual responsiveness.
- The body's self-stabilizing effect is destroyed, and antibodies (or cells) directed against its own tissue components appear to mediate immunity, called autoimmunity. Also known as its own allergy. This is a complex, multi-factor natural phenomenon. In addition to external influences (such as drug haptens, microbial infections), it is also closely related to the body's own genetic factors, especially may be related to abnormalities in immune response genes and immunosuppressive genes in the main histocompatibility system.
Classification of hypersensitivity
- According to the speed of the reaction, it is divided into quick-type hypersensitivity and late-type hypersensitivity. Gail and Combs divide hypersensitivity reactions into the following 4 types:
Hypersensitivity reaction
- Type hypersensitivity is also called anaphylaxis or immediate hypersensitivity. This type of hypersensitivity is characterized by rapid response, rapid regression, obvious individual differences and genetic tendencies, and generally only causes physiological dysfunction without serious tissue damage. Due to the interaction between the antigen and the antibody (usually IgE, some IgG subclasses) on the medium-releasing cells, the IgE Fc on the cell is bridged by fibers, causing cell activation, the intracellular particle membrane and the cell membrane fuse to form a channel, so Some active mediators such as histamine, serotonin, slow-reactive substance-A (SPS-A) are released. These mediators can cause smooth muscle contraction, capillary dilation, increased permeability, and increased glandular secretion. Depending on the target cells acting on these active substances, respiratory allergic reactions, gastrointestinal allergic reactions, skin allergic reactions, or systemic allergic reactions can occur. Common type hypersensitivity reactions are anaphylactic shock, drug-induced drug eruption, food-induced allergic gastroenteritis, pollen or dust-induced allergic rhinitis, and bronchial asthma. [1]
Hypersensitivity reaction
- Type hypersensitivity reaction, also known as cytolytic hypersensitivity reaction or cytotoxic hypersensitivity reaction, is caused by the combination of Ig G or Ig M antibodies with the corresponding antigen on the target cell surface, with the participation of complement, phagocytes and NK cells Pathological hypersensitivity based on cytolysis or tissue damage. For example, blood transfusion reactions that do not match blood types, neonatal hemolytic reactions, and drug-induced hemolytic anemia are all type II hypersensitivity reactions. Hyperthyroidism (Graves disease) is a special type II hypersensitivity reaction.
Hypersensitivity reaction
- Type hypersensitivity is also called immune complex type hypersensitivity or vasculitis type hypersensitivity. It is a medium-sized soluble antigen-antibody complex deposited on the basement membrane of local or systemic capillaries. Neutrophil infiltration is the main feature of inflammatory response and tissue damage. Type III diseases include partial glomerulonephritis after streptococcal infection and exogenous asthma. The Altus reaction is a local type III hypersensitivity reaction. After repeated injections of antigen (such as rabies vaccine, insulin), inflammatory reactions such as edema, bleeding, and necrosis may occur locally. [1]
Hypersensitivity reaction
- Type hypersensitivity is also called delayed hypersensitivity. A pathological manifestation mediated by immune cells. It is mediated by T cells. Common types are: Chemicals (such as dyes) bind to skin proteins or change their composition to become antigens, which can sensitize T cells. Upon re-exposure to the antigen, T cells become killer cells or release lymphokines causing contact dermatitis. Another type is called infectious allergy, which is caused by certain pathogens as antigenic stimuli. It is found in tuberculosis, syphilis, etc. In addition, rejection of organ transplants, encephalomyelitis after vaccination, and some autoimmune diseases are all of this type (see photo).
Hypersensitivity
- In addition to the four types mentioned above, some scholars have proposed type V hypersensitivity reactions (also known as irritative allergies). Type VI hypersensitivity (also known as antibody-dependent cytotoxicity), and even more types. Some allergens (such as penicillin) can also cause different types of hypersensitivity reactions to occur simultaneously in the same individual.
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Hypersensitivity autoimmunity
Causes of hypersensitivity
- The body's self-stabilizing effect is disrupted and antibodies (or cells) against its own tissue components appear to mediate immunity. Also known as its own allergy. The reasons for this are as follows: The emergence of new antigens or the release of the original concealed isolated antigens, which are not tolerated by the immune system, and produce an immune response upon contact (such as release due to trauma). Such as sperm that have not formed before puberty, new antigens formed after viral infection or malignant transformation; 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 to the antigen, exposing some amino acid sequences (which can be used as antigenic determinants) that did not appear before binding, thereby stimulating the body to produce antibodies against its own components. The same can be said for some components in the complement system. The antibodies formed in this way can almost only react with determinants exposed by deformed antibodies or complement. The rheumatoid factor specific to rheumatoid arthritis is the corresponding antibody against the changed immunoglobulin; Because of the immune effect of cross-reactive antigens, it can also stimulate the body to produce an immune response against itself. These cross-reactive antigens may have certain epitopes that are the same as their own components. For example, antibodies to myocardium and endocardium can appear after some strains of streptococcus cause infections (rheumatoid fever).
Hypersensitivity autoimmune disease
- The above-mentioned immune response to self does not need to destroy the original self-tolerance. There are three types of autoimmune diseases caused by the destruction of autotolerance: autoimmune diseases caused by antibodies against autoemulsion determinants, such as autoimmune hemolytic anemia. The disease manifests as destruction of red blood cells and anemia; autoimmune diseases caused by antibodies (eg, thyroid antibodies, gastric mucosal antibodies) directed against its own special tissue components. Multiple antibodies against the tissue can occur in the same patient. It can be seen that the destructive diseases of these tissues and the presence of antibodies do not necessarily cause the disease. It is not yet sure whether antibodies are the primary cause of these diseases; autoimmune diseases, such as systemic lupus erythematosus, caused by antibodies against common components (such as nucleic acids) of various animal tissues.
- There are many hypotheses of autoimmune occurrence, such as: the contraindicated cloning theory believes that, due to immunologically active cell clone mutations or self-stability disorders, forbidden strains that respond to their own tissue components reappear; autoantigen cross-reactivity theory; hapten And autoantigen configuration change theory; inhibitory T cell dysfunction theory and so on.
- Autoimmunity is a complex, multifactorial natural phenomenon. In addition to external influences (such as drug haptens, microbial infections), it is also closely related to the body's own genetic factors. In particular, it may be related to abnormalities in immune response genes and / or immunosuppressive genes in major histocompatibility systems.