Trained immunity is a type of innate brutal immunity.
It all started with BCG. This vaccine is given to newborns to protect them from tuberculosis. They have been doing this for a hundred years, but only recently they began to notice that BCG for some reason helps children to survive with various other infections.
This vaccine is not used everywhere, so we did not immediately understand what was happening.
It seems that BCG stimulates what is called trained immunity. This is a type of innate immunity.
Well, that is, our immunity has a default built-in memory, which is very difficult to work. Immunity remembers the vaccine as a specific infection and then precisely hits it with antibodies or specially trained cells for a real infection. It's tricky and boring.
With trained immunity, everything is more interesting. He is innate, ancient and evil.
This immunity is built not on specialized cells, but on a very primitive animal - on monocytes and neutrophils. These monsters are poorly versed in the intricacies of immunity. They eat stupidly.
Both monocytes and neutrophils literally swallow any stranger. Having tasted someone's blood once, they go berserk and grow an extra row of teeth for themselves to eat even more efficiently.
That is, if they swallow a live or even cut into pieces a bacterium, they turn into serial killers who start looking for a new victim.
It is generally accepted that after the first murder, some relict genes are activated in monocytes with neutrophils, which make them stronger and hungrier.
It would be useful for us, but, unfortunately, small monsters do not live long and take their terrible secret with them to the grave. That is, they will not leave any immunological memory of this massacre. Only creepy legends.
Well, the babies were given BCG, the babies became stronger after that, and then they noticed that in countries where BCG vaccination is practiced, for some reason people get less sick with covid.
There is even an idea that children are also less ill with covid, because they are injected with many different vaccines. The type of vaccination spurs them on innate nonspecific immunity.
Now they are trying to study the BCG vaccine for the prevention of covid. But so far, it seems, have not figured it out yet.
