Crocodiles live rough lives. They live in swamps and rivers that reek with microbes, hunt, kill, and eat animals as large as themselves, and fight each other for territory, food, and mating rights. Even their armor-like scales can’t defend against everything – open wounds are common. And yet, crocodiles rarely get sick.
Like, at all. And the reason is starting to attract interest.
All vertebrates have a two-pronged technique for fighting infections. The first is our innate immune response, an array of relatively simple but fast-acting and reliable defenses. Your skin is part of this immune system, as are many blood proteins and most white blood cells. Our adaptive immune system, however, is slower to react, but more flexible. A handful of specialized white blood cells sniff out infections, capture and memorize the culprits, and start to produce antigen-specific antibodies. The next time the bacteria or virus appears it’s met with an immediate targeted attack. It’s this immunological memory that lets us build up immunities and use vaccines.
The crocodile’s immune system is the same as a humans except that their innate response is insane. If humans have a line of beat cops patrolling their blood, crocodiles have that guy from the Simpsons.
Scientists exposed crocodile serum to twenty-three different strains of bacteria, including several drug-resistant strains such as MRSA. Human serum was able to defeat a total of eight strains – crocodiles killed all twenty-three. When the scientists introduced HIV, the virus responsible for AIDS, the crocodile serum killed a significant fraction of that too.
The proteins in their blood are just that hyperactive. As the scientist Adam Britton put it: “The crocodile has an immune system which attaches to bacteria and tears it apart and it explodes. It’s like putting a gun to the head of the bacteria and pulling the trigger.”
This would explain why crocodiles and alligators are so good at avoiding sickness – the microbes don’t even get a chance to infect them. If we could somehow harness the power of this system we could develop new, stronger antibiotics. And we’re trying, scientists are currently looking into ways to replicate these super-strong proteins. The only problem is that so far high concentrations of this serum tends to be poisonous to human cells too.