Its latest research shows the vitamin calms an over-active part of the immune system in asthma.

BBC: Sunshine vitamin 'may treat asthma'

However, this approach requires drugs to make the virus active and a vaccine to train the immune system to finish it off - this is not just round the corner.

BBC: Analysis: A cure for HIV?

You would think that a chimeric immune system would be more active, not less, and would therefore attack the recipient's other organs, since they look foreign to the transplanted immune cells.

ECONOMIST: Organ transplants

For a T cell to become active, it must receive signals from another part of the immune system called an antigen-presenting cell.

ECONOMIST: Breaching the body's defences

"Everything we already know about fighting off chronic disease, like getting sufficient sleep, staying active throughout life, and having a healthy diet" may stave off premature aging of the immune system, too, Epel said.

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