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Insulin pumps improve the lives

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of many of the 415 million people [br]with diabetes around the world

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by monitoring blood sugar, delivering [br]insulin,

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

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These small machines include a pump and[br]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 [br]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[br]be moved and replaced.

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

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but all bodily implants, [br]at different time scales.

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

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Other implants, such as those used for [br]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 [br]can be expensive and risky.

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This inconvenience happens because of [br]our bodies’ immune systems.

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Honed by several hundred million [br]years of evolution,

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these defensive fronts

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have become exceptionally good [br]at identifying foreign objects.

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Our immune systems boast

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an impressive arsenal of tools to tackle,[br]intercept, and destroy

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anything they believe shouldn’t be there.

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But the consequence of this constant [br]surveillance

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is that our bodies treat helpful [br]implants, like insulin pumps,

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

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

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

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This starts with free-floating proteins

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that stick themselves to the surface [br]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 [br]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[br]with enzymes

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that try to break down the surface [br]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 [br]degrades the object over time.

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If the macrophages are unable to dispatch [br]the foreign body rapidly,

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they fuse together, forming a mass of [br]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[br]layers of dense connective tissue.

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Those enclose the needle that the pump [br]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 [br]impenetrable wall

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that might start to block vital [br]interactions

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between the body and the implant.

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For example, scarring around pacemakers[br]can interrupt

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the electrical transmission that’s [br]crucial for their functioning.

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

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causing immune cells to inflame [br]around these fragments.

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

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However, researchers are finding ways [br]to trick the immune system

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into accepting the new devices we [br]introduce into our bodily tissues.

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

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can dampen the immune response.

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Those basically make the implants [br]invisible to the immune system.

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We’re also making more implants [br]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 [br]completely artificial implant.

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Some medical treatments involve implants

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designed to regenerate lost [br]or damaged tissues.

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

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that will release specific signals,

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and carefully tailor our bodies’[br]immune reactions.

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In the future, this way of working[br]alongside the immune system

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could help us develop completely [br]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 [br]revolutionize medicine–

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and transform, forever, [br]the bodies we live in.