[nudephil (OP)]

Keevan sent us this message:

Is it possible to train a person's immune system outside their body?

For example, if you take blood with B cells and memory cells in it (I assume the blood makes up the immune system but please correct me if I'm wrong) out of the human body, incubate it to keep it alive, healthy and active, then put the COVID-19 virus into it, would it be able to fight off the virus outside the body and gain immunity? Then once it has completely neutralised the virus, put it back into the host person's body giving the person active immunity?

Also why can't active immunity and memory cells from COVID survivers (or survivors of any other virus) be transferred from person to person to give the receiver with a compatible blood type active immunity instead of just passive immunity?

Any takers?

[evan_au]

Is it possible to train a person's immune system outside their body?

There are some experimental cancer therapies which modify immune cells outside the body to make them more aggressive in fighting cancer.
- Cancer is tricky, because it is made of human cells which are hard to distinguish from host cells. And a single cancer contains many different cell lines with different genetics, which makes it hard to target all of them.
- With a virus, it has distinct non-human proteins which are normally easier to to target with a vaccine.
See: https://en.wikipedia.org/wiki/Cancer_immunotherapy

why can't active immunity and memory cells from COVID survivers (or survivors of any other virus) be transferred from person to person

This is a well-developed technique called "convalescent plasma", and it is now being done by blood banks, now there are a number of people who have recovered.
- They don't take whole blood, but only the plasma which contains the antibodies.
- This means that the same person can come back more often than if you take their red blood cells (eg every 1-2 weeks, instread of 3 months).

The donated antibodies only last a few weeks, but that might make the difference between survival or not.
- Researchers are testing to find the most appropriate time to give the plasma:
- Is it when the person is dying on a ventilator?
- Or before they get on a ventilator, so it keeps them off the ventilator?
- The best answer will probably change as the supply of convalescent plasma improves over time.
See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4781783/