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Those of us who started combing the occasional gray hair and were children in the 80s and 90s, we perfectly remember the TV series Once upon a time ... life . Twenty-six episodes of great educational content that showed us every Saturday the ins and outs of the human body in a simple and enjoyable way. For all of us, it is to think of antibodies and instantly visualize some cute beings with wings and antennas that came out of ships that traveled the human body in search of infections.

Now that with the new SARS-CoV-2 it seems that having or not having antibodies against it has almost become a status sign, it is worth reviewing some concepts.

What are the antibodies?

They are defense proteins that type B lymphocytes secrete . Their job is to circulate through the blood throughout our body, while looking for foreign elements such as bacteria and viruses that damage our body. If they locate them, either the antibodies neutralize them directly or they bind to them to mark them and that another part of the immune system is the one that destroys them.

They are all the same?

No. Our bodies make different types of antibodies to defend us against different diseases. Antibodies to the polio virus are not the same as those that protect us against the virus that causes hepatitis B or the bacteria that cause tetanus. That is why the antibodies are said to be very specific .

How many types of antibodies are there?

There are five classes of immunoglobulins or antibodies (it is the same), which are:

Immunoglobulins A (IgA) . They are found mainly in the respiratory tract and digestive system, in addition to tears and breast milk. They are the antibodies responsible for the defense of our mucosa.

Immunoglobulins D (IgD) . They are the most unknown antibodies of all, and are found in small amounts in the blood.

Immunoglobulins E (IgE) . Its presence in blood is residual, except for an extreme reaction of our body to an allergen (anaphylaxis).

Immunoglobulins G (IgG) . They are the most frequent antibodies, and a kind of memory that our body creates to protect us in the future. We can find them in blood and other fluids, protecting us against bacterial and viral infections. They can take time to form after overcoming an infection or after the administration of a vaccine, but are usually detectable in blood from 15-20 days . A positive in IgG against SARS-Cov-2 would indicate that we have suffered and overcome it, or that we are suffering it.

Immunoglobulins M (IgM). We find them in the blood and in the lymphatic fluid. They are the first antibodies that our body makes to put it to fight a new infection. They begin to be detected in blood after 10-12 days.

A positive in IgM against SARS-Cov-2 would indicate that we are in the acute phase of the infection.

How to interpret the results?

IgG (+) and IgM (+) . We have antibodies of both kinds, which would probably indicate that we have contracted the infection in the past few weeks.

IgG (+) and IgM (-) . It would indicate that we are in the final phase of the infection, that we have already passed it or that the vaccine that we have been administered has been successful.

IgG (-) and IgM (-) . We have not had the infection nor are we suffering from it at the moment.

IgG (-) and IgM (+). Our defense system is now beginning to fight a new infection.

The importance of counting

The blood antibody titer, also known as a count, is a laboratory test that will not only tell us whether or not we have antibodies against a certain virus or bacteria; if not, it will also tell us how many antibodies we have.

As we have seen, IgG antibodies are what are going to give us long-term immunity and that is why these are what we are going to look for when we perform this count. It would be advisable to do the test no earlier than four weeks after infection or vaccination, to know how many antibodies our immune system has been able to create.

If the title is low, it means that we have few antibodies in the blood, so we would not be well protected against possible reinfection.

Can they turn against us?

Unfortunately if. Sometimes, without knowing the causes, the body can mistakenly make antibodies against itself, attacking its own healthy cells and organs as if they were a threat. It is what is known as autoimmune diseases. Some examples of them are celiac disease, lupus, psoriasis, rheumatic fever or Crohn's disease.

G antibodies (IgG), do they last a lifetime?

Only in very few cases. For example, the antibodies created against measles or hepatitis B can provide immunity for life, but on the contrary those created against bacteria that cause tetanus or whooping cough last only a few years.

Typically, over the course of months or years, depending on the case, these IgG antibodies weaken until they disappear or cease to be effective.

In the case of SARS-Cov-2, no one knows for sure how long they last, but we could be talking about a duration of at least five months, as evidenced by studies carried out in China.

If we look at viruses similar to this, most patients who have passed SARS continue to have IgG antibodies two years later, and those of MERS were still present one year later.

In accordance with the criteria of The Trust Project

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