Inglese, International

COVID vaccines: how does immunity work?

Vaccines are composed of inactive viruses or bacteria or fragments of these microorganisms which helps to protect the body in future infections. In other words, vaccines are a learning for our immune system, the body reacts to the inactive pathogen creating specific “defenses”.

When we get vaccinated, we create several types of “defenses”. The most important are the antibodies and the memory T cells.

The antibodies are a type of glycoproteins which are part of the “defenses” of the immune system, they are produced by the B lymphocytes. They work by recognizing a specific part of the pathogen, also called antigen. There are different processes that lead to the neutralisation of the pathogen, these are: agglutination, precipitation, opsonization and neutralisation. After the first infection, the body takes some time to react and produce specific antibodies.

The antibodies have a specific immunity, each one identifies one specific pathogen, unless it were a variety of an already known pathogen. We have thousands of types of antibodies and we produce new antibodies when we are infected by an unknown pathogen that hasn’t infected us before. For this reason we are vulnerable to new illnesses.

the antibodies

After the first infection our immune system developes memory. The T cells participate in the inmune reaction producing memory T cells. There are inmature T cells in the bone marrow that migrate to the lymphatic ganglia where are exposed to the antigen. Then they are activated and the clonal expansion begins and they migrate to the infected organ. The T cells eliminate the pathogen and then die of apoptosis. There is a small percentage that remains after the infection, becoming the memory T cells.

These cells are the key of the success of the vaccines. They work as mediators in the following infections recognising the pathogens. After the vaccination, antigens and memory T cells are generated. The antibodies remain in the blood some time after supplying the vaccine and the disappear. The memory T cells remain in the body for a longer time. When we are infected, the memory T cells recognise the pathogen and the inmune reaction starts, producing the antibodies. This second reaction is produced faster due to the previous learning of the vaccines.

Talking about the COVID vaccines. When we see news telling that after four or five months the antibodies levels decrease it is not surprising, since the antibodies are the remains of the natural infection or the vaccines. The key to understand their function is the immunity mediated by memory T cells. These cells are responsible of a milder illness.

Written by Sara García Sánchez

Message to reader: Any information on this blog is for informational purposes only. It is not intended in any way to replace professional figures in the medical and consultancy fields.

Messaggio al lettore: Ogni informazione presente in questo blog è puramente a scopo informativo. Non si intende in nessun modo sostituire figure professionali in campo medico e di consulenza.

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