Healthy living

Vitamin D helps trigger immune system

Zone default image Activates killer T cells

Vitamin D plays a vital role in helping the body fight off infections, new research has found.

The sunshine vitamin has been found to play a crucial role in triggering the body's T cells to fight off invading bacteria and viruses which can cause disease.

For T cells of the immune system to detect and kill invading germs such as clumps of bacteria or viruses, the cells must first be "triggered" into action and change from inactive and harmless immune cells into killer cells that are primed to seek out and destroy all traces of invading germs.

Part of the triggering process involves the T cells having an adequate supply of vitamin D. Without it, the latest research has shown that the T cells remain dormant and fail to react to the invading germs.

Professor Carsten Geisler from the University of Copenhagen who led the study said: "When a T cell is exposed to a foreign pathogen, it extends a signaling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D.

"This means that the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won't even begin to mobilise."

Once activated, the T cells multiply at an "explosive rate" and target the invading germ, leading to its destruction.

Although T cell activation is essential for eradicating invading germs, sometimes the immune system mistakenly reacts to proteins and tissues in the human body, leading to the body launching an attack upon itself. This in turn can lead to various autoimmune diseases.

By understanding how the body's immune system is regulated, it's hoped that new treatments can be developed which can help help prevent this.

Most Vitamin D is produced as a natural byproduct of the skin's exposure to sunlight. It can also be found in fish liver oil, eggs and fatty fish such as salmon, herring and mackerel.

The findings are published in the journal Nature Immunology

This article was published on Mon 8 March 2010

Image © Tomo Jesenicnik -

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