Antigens And Antibodies: What Are They?

The immune system produces antibodies as a result of the detection of harmful agents, called antigens. An antigen is a foreign body that the immune system recognizes as a threat.
Antigens and antibodies: what are they?

Antigens and antibodies are part of the immune system, the former attack it (triggering the activation of an immune response), the latter defend it. Thus, the immune system produces antibodies when it recognizes harmful agents, called antigens.

An antigen is a foreign body to the body, which the immune system identifies as a threat. The wide variety of antibodies that can be synthesized by the organism is due to the random combination of a set of genes that encode the different points of union of antibodies and antigens.

Fascinating, don’t you think? Would you like to know more? In the following lines we describe in detail the difference between antigens and antibodies. 

Antigens and antibodies

Immune response.

Antibodies, also known as immunoglobulins, are activated by the immune system to detect and neutralize foreign bodies, called antigens.

B lymphocytes have the task of synthesizing antibodies in the presence of antigens. The latter can be both substances from the outside and substances formed in the body.

Histocompatibility antigens (HLA) are formed inside the body and are different for each individual, although they are not the prerogative of a single individual. They are found in cells and tissues, so when a cell or organ comes into contact with another person’s lymphocytes, they will recognize the HLAs as foreign and destroy them.

Antibodies are proteins that are synthesized by the immune system when it detects harmful elements, called antigens. Just as there are different types of antigens, there are also different types of antibodies. Each type defends the organism against specific antigens.

Structure of antibodies

The different antibodies have very similar structures to each other since they all contain a protein whose characteristic shape is a “Y”. For this reason the antibodies will look like this letter.

Each type, however, has some differences at the extremity of this protein, which distinguishes the antibodies from each other. This part of the protein is called the hypervariable region, thanks to it an antibody fighting a certain antigen.

When an antibody is found with the compatible antigen, it recognizes it and signals it for others to attack.

What functions do antibodies perform?

Antibodies are responsible for protecting the body, as they are part of the immune system. They attack the foreign body once identified within the body in three ways:

  • By preventing the entry of pathogens into the cell  to prevent them from damaging it.
  • By ensuring that pathogens are eliminated by macrophages and other cells.
  • By directly destroying the pathogen by activating other immune responses.

What does the structure of the antigens look like?

Structure of antigens.

Antigens have a three-dimensional structure and a point where they join antibodies, called the epitope. This means that there are many antibodies for each possible antigen, since the same antigen can have different epitopes.

These assemblage points are a fundamental part of the antigen structure, as they are recognized by a specific antibody and activate the immune response.

Thus, the antigens have some areas called immunodominant. These are points with which most antibodies are compatible.

Function of antigens and antibodies in the immune response

Not all antigens are able to stimulate the immune response, since the latter also depends on antibodies. If they are able to stimulate the immune response, they are called immunogens.

These are substances that the body fails to recognize and therefore rejects. Pathogens with specific antibodies are considered.

Finally, each antibody is assigned a specific antigen, that is, one that is complementary to it. Complementary to be destroyed. given that thanks to this recognition the antibodies activate the immune response capable of destroying the pathogen.

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