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T-cell immunity: what it is and how it helps in the fight against COVID-19
Antibodies are not the body’s only defense against viruses. He has a more powerful weapon – T-cell immunity.
The recent statement by doctors that antibodies remain in the body for about six months in those who have been ill with COVID-19 made many anxious. Indeed, the more time has passed since the moment of recovery, the less antibodies in the blood. Their consistency also decreases. But this does not mean that the body remains defenseless. According to research, virus-specific T cells are produced in those who have undergone a coronavirus infection. They are able to provide long-term immune protection against COVID-19, since, unlike antibodies, they live for several decades.
Long memory
Human immunity is divided into a more solid, deep cellular (it is provided by the T-lymphocytes contained in the blood), and temporary humoral (it is given by antibodies). The system works in this way: T-lymphocytes recognize and destroy the body’s own affected cells, at the same time determining whether the infection is involved. If so, they give a signal about the production of antibodies, which begin to attack the “pest”. After the enemy is defeated, antibodies begin to fade away. And here T-lymphocytes that live in the body for several decadesmemorize the enemy’s face. And when the attack is repeated, the antibodies are again raised on the alarm, but much faster, since they know the strategy. If earlier it took up to a week, now the protection is activated during the first day.
World experience
How long and reliable cellular immunity will be against the SARS-CoV-2 coronavirus is not yet known exactly. T-cell immunity is now being actively studied all over the world, including in Russia. There is little research so far, but there are encouraging results. First, a negative test for antibodies to the SARS-CoV-2 virus does not mean that a person has not had a new coronavirus infection. T-lymphocytes could protect the body. Secondly, the presence of antibodies means (even if there are few of them or they have already disappeared altogether) that specific T cells have formed in the body. True, how viable they are is another question that is now being actively studied all over the world. In some people who have recovered from other types of coronavirus infections (for example, influenza or SARS), T-lymphocytes also recognize the new SARS-CoV-2. That is, there are no SARS-CoV-2-specific T cells yet, but an approximate strategy for protecting lymphocytes is already known.
What’s next
Based on the data that scientists receive when studying the T-cell response, they plan to create test systems… They will determine what infections a person has had, that is, if he has protective T-lymphocytes and to what infections he is vulnerable. It is planned that the test will also be used to assess the effectiveness of the immune response to vaccination.
In some people, the body copes with the virus without activating antibodies or with such a low level of their formation that ordinary laboratory analysis simply will not see them. There may be no clinical symptoms, but the body gains protection from re-infection. How persistent and long, scientists understand.