Sensitization (1)

The adverse effects of chemical substances on human health have attracted increasing attention

The harm of some chemical substances to the human body may be limited to one of the above five kinds, or there may be many of them

In the early days, there was a lot of attention and research on the general toxicity of chemical substances, but in recent decades, in the face of the emergence of multiple toxicological effects of many chemical substances on humans, people should not only study and pay attention to the general acute and chronic toxicity of chemical substances, etc.

1.

Allergens are also called allergens or allergens (allergens, allergens or allergens are medical terms, allergens, allergens or allergens are the corresponding popular terms), which refers to the ability to cause allergies in people Of the antigen

Their common feature is that the body is sensitized after exposure to allergens for a certain period of time

(1) Allergens from different routes

The antigen that induces an allergic reaction is called an allergen, which is a necessary condition for the occurrence of allergies

1.

Inhaled allergens such as pollen, catkins, dust, mites, animal dander, soot, paint, intermediates and reagents

2.

Food allergens such as milk, eggs, fish and shrimp, beef and mutton, seafood, animal fat, penicillin, foreign protein, alcohol, drugs, antibiotics, anti-inflammatory drugs, sesame oil, essence, onion, ginger, garlic and some vegetables and fruits

3.

Contact allergens such as chemicals (reagents and intermediates), daily chemicals (cosmetics, shampoo, detergent, hair dye, soap, chemical fiber products, plastics), metal jewelry (watches, necklaces, rings, earrings), bacteria, fungi, viruses, parasites, UV, ionizing radiation

4.

Injectable allergens such as penicillin , streptomycin , xenogeneic serum and other medicines, as well as insect bites

5.

Allergens can also be produced inside the human body and are called self-tissue antigens or self-antigens
.
Mental stress, work pressure, self-tissue antigens whose structure or composition has changed due to biological or physical and chemical factors such as microbial infections, ionizing radiation, burns, and self-concealed antigens released due to trauma or infection can also become allergens.
Cause a variety of white body immune diseases
.

(2) Complete antigen

According to the nature of the antigen, it is divided into complete antigen and incomplete antigen
.

Complete antigen is immunogenic and immunoreactive substance, such as with most proteins, bacteria, viruses, exotoxin, pollen, animal serum and the like large molecular weight
.
Complete antigen can not only stimulate the body to produce antibodies or sensitized lymphocytes, but also have specific binding reactions with it in vivo and in vitro
.

(3) Incomplete antigen

Incomplete antigens are also called haptens
.
A hapten is a substance that has a small molecular weight and cannot stimulate an immune response.
Once combined with other larger "non-antigenic" substances, it can stimulate an immune response
.
Hapten is an antigen that can bind to the corresponding antibody to cause an antigen-antibody reaction, but cannot alone stimulate the body to produce antibodies
.
It is only immunoreactive, not immunogenic, so it is called an incomplete antigen
.
Most polysaccharides and lipids belong to haptens.
If the hapten is chemically combined with a molecule (carrier) of a pure protein, the pure protein will acquire new immunogenicity and stimulate the human body to produce corresponding antibodies
.
Once the hapten binds to the pure protein, it forms an antigen cluster of the protein
.
When hapten enters an allergic body, it can bind to tissue proteins in the body and become a complete antigen.
This complete antigen can cause hypersensitivity reactions
.

Generally speaking, B lymphocytes recognize haptenic determinants, and T lymphocytes recognize carrier epitopes
.
The former is the humoral immune mechanism, and the latter is the cellular immune mechanism
.

(4) Antigenic determinants

Antigenic determinants are specific chemical structures (including chemical groups and molecular conformations) on the surface of an antigen that can induce the production of specific antibodies.
The antigen binds to the receptors on the surface of the corresponding lymphocytes to trigger an immune response and immune response
.

Generally, antigenic determinants are composed of 6-12 amino acids or carbohydrate groups, which can be composed of continuous sequences (primary protein structures) or discrete three-dimensional protein structures
.
Most of the antigenic determinants exist on the surface of the antigenic substance, and some exist in the interior of the antigenic substance, and must be exposed after enzymatic or other treatments
.

Antigen-antibody binding is highly specific, that is, an antigen molecule can only react with the antibody produced by its stimulation
.
The specificity of the antigen depends on the number, nature and spatial configuration of the antigenic determinants, while the specificity of the antibody depends on the ability of the variable region of the antibody immunoglobulin Fab segment to bind to the corresponding antigenic determinants
.
The combination of antigen and antibody is not done through covalent bonds (some highly toxic effects and "triple effects" are often done through covalent bonds), but there must be a "lock and key" relationship, but also through spatial structure The mutual adaptation and weak short-distance gravitation are combined, such as van der Waals gravitation, electrostatic gravitation, hydrogen bonding and hydrophobic interaction
.

(5) The nature of the antigen and the characteristics of antigenicity

1.
Three properties of antigen

Antigens have three properties; foreign body, macromolecular and specificity
.
Only antigens can cause specific immunity
.
Allergens do not necessarily have these three properties.
If allergens are to cause an allergic reaction in the body, when the allergen enters or contacts the body of the allergic constitution, it needs to bind to the tissue proteins in the body to become a complete antigen, and then it will have foreign body properties and macromolecules.
Sex and specificity
.
For example, dust, cold wind, ultraviolet rays, etc.
are allergens to some people, but they are not direct antigens, because dust, cold wind, ultraviolet rays, etc.
do not satisfy the three properties of antigens, such as macromolecularity, specificity, and foreign body.
Only these allergies The original causes changes in some structure or composition of the allergic constitution to produce self-tissue antigens
.
It can also be said that allergens such as dust, cold wind, and ultraviolet rays are the antigens that cause allergies
.

On the whole, allergens are part of antigens, and allergens are a subset of antigens
.
Allergies are damage to the body caused by individuals who have produced antibodies receiving the same antigen again
.
The allergen that causes the allergic reaction must be an antigen or an indirect antigen, and the antigen is not necessarily an allergen
.

2.
Two basic characteristics of antigenicity

Antigenicity has two basic characteristics, namely immunogenicity and immunoreactivity
.

Immunogenicity: The ability to stimulate and induce immune system responses, make the body produce antibodies or sensitize lymphocytes, and induce humoral or cellular immunity
.

Immune reactivity: the ability to react with the product of an immune response and specifically bind to antibodies or sensitized lymphocytes to cause an immune response
.

Substances with immunogenicity and immunoreactivity are antigens
.
Immunogenicity and immunoreactivity are sometimes collectively referred to as antigenicity
.

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