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[Inside the thymus]
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Our immune system fights
infections and cancer cells,
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with a type of white blood cell,
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the T cell.
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T cells are made in an organ
called the thymus.
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Immature blood cells are made
from blood stem cells in the bone marrow,
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travel through the bloodstream
to the thymus.
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Inside the thymus, over the course
of approximately 2 weeks,
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a network of different cells
impart chemical signals
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that affect the fate
of the immature T cells.
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They're guided through
a process of development,
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selection,
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and also elimination
to become mature T cells.
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Firstly, the immature T cells
are instructed to develop receptors.
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At the next stage,
those cells with receptors
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that can respond to the type of proteins,
the ones useful to our immune system,
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are signaled to survive.
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The rest are eliminated.
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After this stage,
some of the developing T cells,
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they recognize proteins
from the healthy cells of our own body
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which can be dangerous
and cause auto-immunity,
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where they may target
those cells and tissues.
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In the final stage,
these cells are eliminated.
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The remaining now matured T cells,
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which have passed
through the selection process,
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enter the bloodstream
and become part of our immune system.
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In fact, as little as one percent
reach this stage
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and are now ready to protect
against harmful infection and disease -
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but not the healthy cells of our own body.
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From a young age our thymus
degenerates, getting smaller.
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Throughout our lives,
fewer and fewer T cells are made,
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reducing our protection against
new infections and cancer,
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especially, in old age.
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Finding ways to regenerate the thymus
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could help to boost the immune system
when this happens
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and could also lead to treatments
for a number of conditions
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affecting both the thymus
and the immune system.
