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Insulin pumps improve the lives

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of many of the 415 million people 
with diabetes around the world

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by monitoring blood sugar, delivering 
insulin,

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and preventing the need for constant 
finger-pricking and blood testing.

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These small machines include a pump and
a needle which can sense glucose levels;

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feed back to the pump;

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and then calculate how much insulin 
to deliver through the needle.

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But they have a catch: they’re temporary.

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Within a few days, glucose sensors have to
be moved and replaced.

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And it’s not just glucose monitors and 
insulin pumps that have this problem,

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but all bodily implants, 
at different time scales.

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Plastic prosthetic knees have to be 
replaced after about 20 years.

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Other implants, such as those used for 
cosmetic reasons,

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can meet the same fate in about 10.

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That isn’t just a nuisance: it 
can be expensive and risky.

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This inconvenience happens because of 
our bodies’ immune systems.

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Honed by several hundred million 
years of evolution,

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these defensive fronts have become

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exceptionally good at identifying
foreign objects.

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Our immune systems boast an impressive 
arsenal

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of tools to tackle, intercept, and destroy

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anything they believe shouldn’t be there.

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But the consequence of this constant 
surveillance

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is that our bodies treat helpful 
implants, like insulin pumps,

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with the same suspicion as they would
a harmful virus or bacteria.

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As soon as the insulin pump has been 
implanted in the skin,

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its presence triggers what’s known as a
“foreign body response.”

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This starts with free-floating proteins

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that stick themselves to the surface 
of the implant.

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Those proteins include antibodies,

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which attempt to neutralize the new object

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and send out a signal that calls other 
immune cells to the site

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to strengthen the attack.

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Early-responding inflammatory cells,

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like neutrophils and macrophages,

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respond to the emergency call.

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Neutrophils release little granules filled
with enzymes

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that try to break down the surface 
of the insulin pump’s needle.

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Macrophages secrete enzymes too,

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together with nitric oxide radicals,

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which create a chemical reaction that 
degrades the object over time.

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If the macrophages are unable to dispatch 
the foreign body rapidly,

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they fuse together, forming a mass of 
cells called a “giant cell.”

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At the same time, cells called fibroblasts

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travel to the site and begin to deposit
layers of dense connective tissue.

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Those enclose the needle that the pump 
uses to deliver insulin

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and test for glucose levels.

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Over time this scaffolding builds up,

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forming a scar around the implant.

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The scar functions as an almost 
impenetrable wall

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that might start to block vital 
interactions

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between the body and the implant.

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For example, scarring around pacemakers
can interrupt

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the electrical transmission that’s 
crucial for their functioning.

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Synthetic knee joints may give off 
particles as they’re worn down,

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causing immune cells to inflame 
around these fragments.

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Tragically, the immune system’s attack
can even be life-threatening.

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However, researchers are finding ways 
to trick the immune system

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into accepting the new devices we 
introduce into our bodily tissues.

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We’ve discovered that coating implants 
with certain chemicals and drugs

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can dampen the immune response.

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Those basically make the implants 
invisible to the immune system.

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We’re also making more implants 
out of natural materials

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and in forms that directly mimic tissues,

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so that the body launches a weaker attack

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than it would if it came across a 
completely artificial implant.

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Some medical treatments involve implants

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designed to regenerate lost 
or damaged tissues.

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In those cases, we can design the implants
to contain ingredients

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that will release specific signals,

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and carefully tailor our bodies’
immune reactions.

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In the future, this way of working
alongside the immune system

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could help us develop completely 
artificial organs,

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totally integrative prostheses,

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and self-healing wound therapies.

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These treatments might one day 
revolutionize medicine–

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and transform, forever, 
the bodies we live in.