The Difference Between Antigen and Antibody


Sometimes you may know what is antibody and what is antigen. However, can you be sure that you are able to point the difference between antigen and antibody? If not, you can find the answer in this article.

antigen and antibodyBody

What is antigen

Antigen is a substence, which can stimulate the immune system and induce an immune response. Such as antibodies or sensitized lymphocytes specifical reaction. A complete antigen should be including two parts: immunogenicity and immunoreactivity. The first refers to the substance, which is capable of inducing a host cell to produce an immune response; the second one is also known as reactogenicity, it refers to the antigen, which can react with antibody or sensitized lymphocytes. Some substances, which alone can just have the reactogenicity no immunoreactivity, are called hapten; however immunogen usually has both immune response capability.

What is antibody

Antibody is always called immunoglobulin(Ig). It refers to the immunoglobulin, which have antibody activity and antibody-like structure. Ig, which is about 20% of plasma protein, is produced by plasma cells, existing in blood and other body fluids. Ig structure has heterogeneity, it can be divided into different types; A majority of Ig have antibody activity, they can specifically recognize and bind antigen, and produce a series of biological reactions.

Immune functions of the antibody

Antibody binds to a specific antigen to occur biological effects, the ultimate physiological function is mainly anti-infection, the mechanism can be classified as following aspects:

  1. Toxin neutralization

When the antigen is a bacterial toxin, it binds to the antibody, then they can neutralize toxicity of the host cell. When the antigen is a hormone or enzyme, it binds to the antibody, so it may also be losing its toxicity.

  1. Infection of neutralization

When the virus bind to the corresponding antibody, it may lose its ability to invade into host cells to reproduce.

  1. Phagocytosis conditioning

After antibacterial antibody combined with bacteria, although it can not directly eliminate the cells, being used as the conditioning factor, which promotes phagocytosis of immune cells to engulf bacteria.

  1. Induced lysis

After IgG antibody and IgM antibody bind] to bacteria, they can activate the classical complement activation to lysis pathogens.

  1. Antibody-mediated ADCCIgG class can also mediate NK cells produced to ADCC effector, then it can kill virus-infected target cells and malignant cells.

All in all, sometimes antigen and antibody are very hardly to be separated. We can just tell them from each other by their origins.

These are the main defferences between antigen and antibody. I am not sure if this is helpful for you. But I can be sure that this must let you know more about the two substances.


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