Vitamin plays 'crucial' immune system role

The discovery could help in the development of new vaccines and ways to combat auto-immune diseases and cancer.

It is well known that vitamin D is vital for calcium absorption and bone health, and some studies have suggested it has an anti-cancer effect. But until the new research scientists had not realised what a crucial role it played in the immune system.

A team of Danish scientists found that vitamin D can transform inert T-cells – one of the body’s infection-fighting white blood cells – into “killer” cells that seek and destroy unwelcome invaders. Without vitamin D, the cells remain dormant and unable to respond to threats.

The mechanism through which the vitamin primes T-cells involves chemical changes that allow the cells to recognise and respond to harmful foreign proteins.

Some of the T-cells that are activated by vitamin D become “killer” cells, one of the most potent weapons in the immune system. They attack and destroy anything carrying traces of target molecules, including cancer cells. Others turn into “helper” cells that enable the immune system to acquire a “memory”. They send messages about the target to other immune cells so they can recognise it again.

The Danish scientists carried out laboratory tests with human T-cells which showed how vitamin D was needed to trigger a vital signalling enzyme.

Without this signal, T-cells were not activated when exposed to traces of foreign invaders.

Prof Carsten Geisler, from the University of Copenhagen, who led the research reported in the journal Nature Immunology, said: “Scientists have known for a long time that vitamin D is important, but what we didn’t realise is how crucial vitamin D is for actually activating the immune system – which we know now.”