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Our immune systems are  incredible disease-fighters,   thanks in no small part to  proteins called antibodies. Their job is simple: grab onto things your body  wants to get rid of, and only those things.

This act alone can be enough to  prevent a virus from infecting a cell,   or stop a toxin from working. And even if not, it flags the problem so your  immune cells know what they need to deal with. In fact, antibodies are so powerful that  doctors and scientists use them a lot—to   detect specific molecules, tackle  diseases, and even treat snakebites!

And they have the potential to do much, much more. Antibodies are also called immunoglobulins,  and they’re Y-shaped proteins with sticky tips. They’re made by a special kind of white  blood cell called B lymphocyte or B cell.

And your body has billions  of different B cells in it. So right now, you’re capable of  making billions of unique antibodies. That’s why your immune system can  fend off so many different attackers.

Though, you aren’t producing  all those antibodies at once. Most of your B cells are “immature”,  which means they’re just kind of sitting   around with the special antibodies they  produce embedded in their outer membrane. They wait this way until something  sticks to one of those antibodies.

That tells the B cell there’s something  out there for its antibody to grab! So it “matures” and starts ramping up production. We call that “something” an antigen,   no matter what it is — a bit of a  virus, a toxic protein, whatever.

Like, nowadays, we use the sticking  power of antibodies in pregnancy tests! Animals, or, more recently, cells  are used to make antibodies which   bind to the hormones that signal pregnancy. And those are the detection part  of your at-home pregnancy test!

Similar tests exist for things  like drugs and pathogens. Now, especially when it comes to  using antibodies to fight disease,   it’s important to note that antigens are small. That’s because the sticky part of an  antibody is only a few nanometers wide.

Meanwhile, the viruses that  infect us tend to be one or two   orders of magnitude larger — and  bacteria are even larger than that! So a single pathogen has many potential antigens,  or places where different antibodies could attach. Some of those antibodies may  be more effective than others   at actually stopping the  pathogen from causing harm.

We call those neutralizing antibodies…  because they neutralize things. But neutralizing or not, once antibodies  are floating around in the blood,   their sole job is to stick to their antigens. That way, if nothing else,   other immune cells can spot them and  destroy whatever they’re attached to.

Now, once your body’s dealt with a problem,   some of the B cells that were called  to arms become memory B cells. Essentially, they go back  to waiting, but the body is   extra careful to make sure they stick  around in case the offender shows up again. This is how vaccines work!

The only real difference is that,  to generate those memory B cells,   they use part of a pathogen or a weakened  one in place of a full-on infection. But sometimes, the process of ramping up antibody  production is too slow or not robust enough. And it's thanks to those cases that scientists and   doctors first figured out how  to use antibodies as medicines.

Antibody-based medicines only really became  a thing at the end of the 19th century. One of the biggest breakthroughs happened  in 1890, when two scientists set out to find   a treatment for diphtheria — a bacterial  disease that was killing a lot of people. These particular bacteria release   deadly toxins that can kill a person before  their immune system can clear the infection.

Now, at the time, no one knew about  antibodies. That wasn’t a term yet. What they had figured out was that animals  could develop a resistance to toxins.

They then showed that whatever  it was that made them resistant   could be found in the fluid part of their blood. So they tried giving this fluid,  called serum, to other animals. And it saved those animals from an  otherwise deadly dose of the toxins.

The next logical, if risky, step  was to try the same thing in people. So, the team injected the  diphtheria toxins into horses,   waited a bit, and then took some of their  blood and removed the actual blood cells. The resulting serum was then transfused  into human patients with the disease.

And the treatment was so successful  that it won the first ever Nobel Prize   in Physiology and Medicine in 1901! Around that time, scientists tried the  same kind of thing to treat snakebites. Much like diphtheria toxins,  by the time the body ramps up   antibody production to neutralize snake  venom toxins, it’s often too late.

So scientists invented antivenoms: the cleaned-up  serum from animals injected with venoms. And they work by boosting the amount of  venom-neutralizing antibodies in a person’s blood. That said, there is a catch to using  other animals to make antibodies:   these treatments also tend to contain  other proteins from the animals.

And when our immune system  sees those, they can trigger   a separate immune response — one that can cause  nasty side effects or be life-threatening. One way around this is to use convalescent plasma. It’s essentially the same sort of  antibody-packed serum, but from people.

Since the blood is human, there’s  less likelihood of a bad reaction. And in the early 20th century,  convalescent plasma was used for   all sorts of diseases — including,  famously, the global flu pandemic of 1918. Then, it somewhat fell out of favor,  because antibiotics became a thing.

It’s always considered an option,  though. Like, we tried it for MERS,   SARS, ebola, and most recently, COVID-19. But by and large, antibody-based medicines  have moved beyond using actual blood.

That’s because, in 1975, antibody researchers  had another Nobel Prize-winning breakthrough. They fused a B cell with a  rapidly-reproducing blood cancer cell. That allowed them to make lots  of copies from that B cell — and,   in turn, a large, pure sample  of the cells’ antibodies.

This was the beginning of monoclonal  antibody treatments, which are now   all the rage in medicine. Remember: the immune system doesn’t just  make one type of antibody per invader. It makes tons of different ones,  some of which are better than others.

With blood-based treatments,   you’re stuck with whatever antibodies happen  to be in there in whatever concentration. But monoclonal methods allow you to  produce lots of a really good antibody,   so the medicines are more potent  and have fewer side effects. The first therapeutic monoclonal antibody   was approved in 1986 to stop kidney transplant  patients from rejecting their new organ.

And as of January 2020, just under 80 other  monoclonal antibody drugs have been approved   in the US, including ones for cancer,  rheumatoid arthritis, Crohn’s disease,   psoriasis, migraines, and asthma. We’ve been tapping into the incredible  power of antibodies for over a century. And in that time, we’ve gotten  better and better at making them.

Nowadays, the hardest part is finding  a great antibody to mass produce. And that’s where a lot of  the research is focused now. Unfortunately, we’re out of time!

So  if you want to learn more about that,   you’ll have to wait for another day. Like… tomorrow! Because this is just the first of  three episodes in our mini-series on antibodies!

Tomorrow’s episode will dive into  how scientists find and create   the best monoclonal antibodies for use in  medicines and things like pregnancy tests. Then, in our last installment,  we’ll talk about what the future   of antibody-based technologies might look like. We hope to see you tomorrow!

And if you  want to make sure you don’t miss an episode,   be sure to subscribe and  ring that notification bell. {♫Outro♫}.