Let's talk vaccines: ᴬⁿᵗⁱᵍᵉⁿˢ ᵃⁿᵈ ᴬⁿᵗⁱᵇᵒᵈⁱᵉˢ

Let's first discuss antigens. What are antigens?

We would tell children, for simplicity's sake, that antigens are germs. They are what make us sick. And we would be right but antigens are a lot more complex than calling them germs.

Antigens, also called immunogens, invade our immune systems and try to diminish our health. When they enter us they are an alert to our immune system that it is being invaded and needs protection.

There are two kinds of antigens. Foreign and auto.

Foreign antigens are exactly what you would suspect. Anything outside of your body that could upset your immune system. And those antigens could be bacterial or viral depending on their origin. Some examples include snake venom, E. coli, COVID, pollen.

Autoantigens originate in the body and do not usually provoke an immune response, except in individuals with autoimmune disorders.

The presence of antigens rouses illness-fighting white blood cells, called lymphocytes. This presence of antigens causes white blood cells to make cells called antibodies to fight against the antigens.

The battle for health has begun.

Antigens entering the body send a warning signal to the immune system. And production by B cells (a type of lymphocyte, or white blood cell) begins. What are B cells producing? Antibodies to fight the antigens.

An antibody (also known as immunoglobin) is a type of protein and there are five specific types, each type of antibody can only bind to one type of antigen. Antibodies are made up of four polypeptide chains, which are arranged in a Y-shape. The constant region is always the same, but the variable region is different depending on the type of antibody. The antigen binds to the antigen binding site at the end of the variable region.

Once the antibodies find the antigen, they bind to it. This triggers a series of actions by the immune system that, ultimately, leads to the destruction of the pathogen or tags it so other immune cells will recognize it.

Here's a quick rundown on the 5 types:

▪️Immunoglobulin G (IgG): This type accounts for around 75% of all antibodies in the human body. They detoxify harmful substances and provide long-term protection.

▪️Immunoglobulin A (IgA): This one is found primarily in mucosal tissues, such as those in the mouth, vagina, and intestines, as well as in saliva, tears, and breast milk. It accounts for 15% of all antibodies in the human body. These antibodies collect antigens and remove them from your body in your mucus or other body fluids.

▪️Immunoglobulin M (IgM): These are the first antibodies made by B cells in response to antigens.

▪️Immunoglobulin E (IgE): This is the antibody responsible for the allergic response that is mostly found in the lungs, skin, and mucosal membranes.

▪️Immunoglobulin D (IgD): This type accounts for only around 0.25% of antibodies in the human body. IgD is important in the early stages of the immune response. Unlike other antibodies, it does not actively circulate but instead binds to B cells to instigate the immune response.

There are two types of man-made antibodies, polyclonal and monoclonal. Both types are laboratory-produced molecules that act as substitute antibodies that can restore, enhance or mimic the immune system's attack on cells.

What happens when the antigen and the antibody meet?

They form a relationship, a close one, called an antigen-antibody complex (also known as an immune complex). The complex works like a lock and key mechanism.

 

 

Once the complex is formed it goes through one of the following steps:

▪️Agglutination: Here, antibodies clump the antigens together which are later destroyed by phagocytes (a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles). Thus by clumping them together, phagocytes can detect them more easily.

▪️Precipitation: Here, soluble antigens are precipitated and destroyed by the phagocytes.

▪️Opsonization: In this method, antibodies are coated on microbial surface after which antigen locks in. This makes it more susceptible to phagocytosis.

▪️Neutralization: Here, antibodies blocks or neutralizes the harmful chemicals produced by antigens. These are later destroyed again by phagocytosis.

▪️Complement Activation: Once the lock and key mechanism perfectly fits into the place, it leads to cell lysis (the disintegration of a cell by rupture of the cell wall or membrane.)

The ratio of antigen to antibody determines size and shape of immune complex. This, in turn, determines the effect of the immune complex.

The distinct functions of antigens and antibodies are used to create tests and vaccines that help detect and combat illness and disease.

Once the antigen turned pathogen is destroyed and the person recovers, a few of the B cells that produced the antibodies stick around. These are known as memory cells because they remember the pathogen and can quickly produce new antibodies against it.

If the memory cells encounter the pathogen a second time, the immune system can fight it off much more quickly. By doing this, they can get rid of the pathogen before the person even becomes sick. When this happens, the person is said to be immune to that particular pathogen.

Vaccines boost the number of antibodies in your body against a specific antigen. When a vaccine enters your body, your B-cells respond as if a naturally occurring antigen has attacked your body. The B-cells respond to the vaccine by reproducing themselves to form an army of cells that are programmed to react to the antigens in the vaccine.

The antibodies created by the vaccine lie dormant in your body until you contract an infection from that antigen, and then they are called to action.

If you contract an infection, antibodies called memory B cells quickly reproduce and make the specific antibodies you need to destroy that antigen.

The memory B-cells’ response is called a secondary immune response, and it’s much faster and more effective than the reaction your body would have to the infection if you had not been vaccinated.

{You can find all the sources I used by clicking here.}