New Scientist - 10.08.2019

12 | New Scientist | 10 August 2019

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PEOPLE having organ transplants

in future may not have to take

anti-rejection medicines, thanks

to a technique that could make

their immune system see the

donor’s tissue as their own.

The method involves giving the

recipient an infusion of the donor’s

cells a week before the operation,

so it wouldn’t work for those

getting an organ from someone

who has died. But it would be

suitable for those with a living

donor, such as in some kidney,

liver and pancreatic cell

transplants.

When the technique was tested

on five macaque monkeys, the

transplanted pancreas cells stayed

healthy without being rejected

for up to two years. “It’s still very

early days, but if it works, it’s a

complete game changer,” says

Chris Callaghan at Guy’s and St

Thomas’ Hospital in London,

who wasn’t involved in the study.

Transplants of organs such as

kidneys, livers and hearts can be

life saving, but recipients have

to take medicines for the rest of

their lives to damp down their

immune system and avoid the

new organ being rejected. These

drugs have serious side effects,

such as leaving people more

prone to infections and cancer. So

a way to force someone’s immune

system to accept a donated organ

has been sought for decades.

Bernhard Hering at the

University of Minnesota and

his colleagues exploited the way

that our immune systems learn

not to attack our own cells.

Throughout our lives, cells

naturally die through a process

called apoptosis and are shed into

the bloodstream. Immune cells

in the spleen take them in and

“remember” that their molecules

signify the body’s own cells – not

invading microbes – and so should

be tolerated. It is possible to

mimic this process by treating

cells with a chemical called ECDI

that triggers apoptosis.

Hering and his team induced

a condition similar to type 1

diabetes in five macaques. They

then treated these monkeys with

pancreatic cell transplants from

donor monkeys.

A week before the transplant,

each sick monkey was given an

infusion of ECDI-treated blood

cells from a donor. They received

another dose a day after the

transplant, and they were also

given anti-rejection drugs for

three weeks.

Even after these drugs were

stopped, the cell transplants stayed

healthy and produced insulin for

two years in one animal – the

point at which the study ended –

and one year in the rest (Nature

Communications, doi.org/c82k).

The approach could eventually

be used in people who receive

a kidney or part of a liver from

a living donor, says Hering. In

the UK, about a third of kidney

transplants come from such

donors, who are usually relatives

or friends. ❚

Medicine

Clare Wilson

AGE FOTOSTOCK/ALAMY STOCK PHOTO

Rejection-free transplants

We may be able to train the body not to attack a donated organ

Zoology

Bees’ hairy tongues

help them mop up

thick or thin nectar

BUMBLEBEES can gorge on gloopy

nectar just as easily as they can

slurp up the runny kind – and now

we know why. It is all down to tiny

hairs on their tongues.

A close look at a bee’s tongue

reveals a long, rod-like stalk

that is covered in thin, hair-like

protrusions. This makes it look a

little like a tiny mop, which the bee

dips in and out of a flower to drink

sweet nectar.

Pascal Damman at the University

of Mons in Belgium and his

colleagues analysed videos of

buff-tailed bumblebees (Bombus

terrestris audax) feeding on nectar

of different viscosities, and made

an unexpected discovery.

They found that regardless of the

fluid’s thickness, the bees lapped

it up at an identical rate, collecting

the same volume of liquid each time

they inserted their tongue. That is a

surprise because, in theory, thicker

liquids should be more likely than

thin ones to stick to an object dipped

into the solution.

The researchers 3D printed

rods that were either smooth or

covered in tiny structures to mimic

the bees’ hair-like protrusions.

They then dipped the rods into

fluids of different viscosities.

It turned out that the distance

between the microstructures on the

rods explained the puzzle. If they

are spaced close enough to one

another, then liquid is automatically

pulled between them by what is

called capillary action. This process

is fast enough to fill all the gaps

with nectar each time the bee dips

its tongue in, and holds the liquid

so it doesn’t drip (Soft Matter,

doi. org/c82q).

This means bees can cope even if

the nectar’s viscosity changes. “You

don’t want to starve just because

your meal has gotten thinner,” says

Patrick Spicer at the University of

New South Wales, Australia, who

wasn’t involved in the study. ❚

Ruby Prosser Scully

This bee (Perdita

halictoides) has

a hairy tongue

that may help it

to eat different

types of nectar

NATURE COLLECTION/ALAMY

Recipients of donated

organs have to take drugs

to avoid rejection

“Even when the anti-

rejection drugs were

stopped, the transplants

stayed healthy”