Vitamin D Crucial to Activating Immune Defenses...

Scientists at the University of Copenhagen have discovered that
Vitamin D is crucial to activating our immune defenses and that without
proper intake of the vitamin, the killer cells of the immune system (known
as T cells) will not be able to react sufficiently and fight off serious
infections in the body.

For T cells to detect and kill foreign pathogens such as clumps
of bacteria or viruses, the cells must first be 'triggered' into action
and 'transform' from inactive and harmless immune cells into killer
cells that are primed to seek out and destroy all traces of a foreign
pathogen.The researchers found that the T cells rely on vitamin D
in order to activate and they would remain dormant, unresponsive
to the possibility of threat if vitamin D is lacking in the blood.

Chemical Reaction that Enables Activation...
In order for the specialized immune cells (T cells) to protect the
body from dangerous viruses or invading bacteria, the T cells
must first be exposed to traces of the foreign pathogen. This
occurs when they are presented by other immune cells in the body
(known as macrophages) with suspicious cell fragments or traces
of the pathogen. The T cells then bind to the fragment and divide
and multiply into hundreds of identical cells that are all focused on
the same pathogen type. The sequence of chemical changes that
the T cells undergo enables them to both be sensitized to and able
to deliver a targeted immune response.

When a T cell is exposed to a foreign pathogen, it extends a
signaling device acting like an antenna (known as a vitamin D
receptor) to search 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 cannot begin to mobilize.

T cells that are successfully activated transform into one of two
types of immune cell. They either become killer cells that will attack
and destroy all cells carrying traces of a foreign pathogen or they
become helper cells that assist the immune system in acquiring
memory.The helper cells send messages to the immune system,
passing on knowledge about the pathogen so that the immune
system can recognize and remember it at their next encounter.
T cells form part of the adaptive immune system, which means
that they function by assisting the immune system to recognize
and effectively adapt to constantly changing threats.

The researchers wrote "Scientists have known for a long time that
vitamin D is important for calcium absorption and the vitamin has
also been implicated in diseases such as cancer and multiple
sclerosis, but what we didn't realize is how crucial vitamin D is
for actually activating the immune system, which we know now."

Identifying the Role of Vitamin D in the Activation of T Cells
Has Been a Major Breakthrough...

The discovery provides much needed information about the
immune system and will help scientists regulate the immune
response. This is important not only in fighting disease but also
in dealing with anti-immune reactions of the body and the rejection
of transplanted organs. Active T cells multiply at an explosive rate
and can create an inflammatory environment with serious
consequences for the body. As an example after organ transplants,
T cells can attack the donor organ as a foreign invader.

In autoimmune disease, hypersensitive T cells mistake fragments
of the body's own cells for foreign pathogens, leading to the body to
launch an attack upon itself.

The research team was also able to track the biochemical sequence
of the transformation of an inactive T cell to an active cell, and thus
would be able to intervene at several points to modulate the immune
response. Inactive T cells crucially contain neither the vitamin D
receptor nor a specific molecule (PLC-gamma1) that would enable
the cell to deliver an antigen specific response.

The researchers believe "the findings could help us to combat
infectious diseases and global epidemics, particularly useful when
developing new vaccines."

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 or taken as a dietary
supplement.

Journal Reference: Nature Immunology, 2010
von Essen et al. Vitamin D controls T cell antigen receptor signaling
and activation of human T cells.