modern medicine has an impressive arsenal.

And one of its most versatile weapons

are Y-shaped proteins called monoclonal antibodies.

Our immune systems already produce

their own antibodies.

They come in billions of variations,

each matching a specific target,

such as a particular toxin, bacteria or virus.

When they bind to their target, they send a signal…

This bacterium is now marked for destruction.

These naturally-produced antibodies are pretty effective,

but in the 1970s,

scientists figured out how to mass produce them.

They can take any specifically-targeted antibody

and make huge numbers of identical clones,

which means you can produce monoclonal antibodies,

for almost any disease you can think of.

Which brings us on to cancer…

Mutated cells that start growing out of control

can be deadly.

But, the body's immune system

isn't defenceless.

Meet the CTL.

It's a type of white blood cell

that can detect infected or mutated cells,

and when it finds one, it secretes toxic molecules

that initiate a self-destruct sequence.

But the CTLs do sometimes need to be reined in.

If they get overenthusiastic

the immune system can start causing collateral damage

– attacking healthy cells.

Fortunately, the CTLs can be turned off

by activating a molecule called PD1.

The trouble with having an 'off-switch'

is that cancer cells can exploit it.

Many cancer cells protect themselves

with a counter receptor called PD-L1.

This is where monoclonal antibodies come in.

Scientists can use one of two types:

one that binds the PD-1 molecule,

or another that goes for PD-L1.

Thanks to the monoclonal antibodies,

all of the CTLs are fully activated

and can blast away the cancer.

This is just one way

that monoclonal antibodies can be used.

They've already proven effective

against a whole range of cancers

and yet more are still being developed.

With their ability to be targeted at specific diseases,

monoclonal antibodies

are turning out to be a game-changer,

and one of our most effective weapons

in the fight against cancer.