Adventures with the Fabulous mAb, Part Two

In our previous piece, you heard my accolades for the world’s smartest molecule, the one that can’t be fooled, the monoclonal antibody. It resides in our assays for infectious disease and is found in recreational drug tests (which are also commonly utilized in veterinary practice). What else can mAbs accomplish? I’m so glad you asked! The mAb can be trained to identify virtually anything you want to test for. It’s not limited to positive and negative results (i.e., blue vs. white); it can also measure the exact quantity of a substance present in the sample, yielding a number which indicates how dire the situation is. It can even be used to sort individual cells as they pass through a machine, to compile a pure sample of cells with desirable qualities, which are then used for bone marrow transplants. It’s like picking out the best oranges as they pass on an assembly line. It can be bound to dyes or fluorescent material and applied to biopsy samples. This allows the pathologist to identify substances or specific cells in a tiny piece of tissue that would not otherwise be visible, no matter how high-powered the microscope. It’s like applying a paint that only sticks to cancer cells. It’s like those old Scooby Doo episodes where the culprit is found because he walked through fluorescent powder. If you have the right test components, the answer can be as easy as switching on a blacklight.

Antibodies are all over the place inside the body of every vertebrate animal. Every time the immune system meets a new invader, its machinery gets right to work building a custom-made arsenal of antibodies. They’re very effective at repelling intruders, but it is a rather slow manufacturing process. If the enemy is vicious enough, you might die before you get the chance to deploy your new antibodies. Such is the case with rabies, botulism, and venomous snake bites, among others. In these cases, doctors rush to inject the previously manufactured antibodies from someone other than the patient. It works: this is the concept behind antitoxins and antivenins. Snake venom, for example, is injected into a horse or sheep in tiny amounts, not enough to kill. Over several weeks, a good crop of antibodies is produced which can then be harvested for use on ER patients who have tangled with a snake. Of course, antibodies being antibodies, one must know precisely which species of snake did the deed, else the doctor won’t be able to choose the appropriate antivenin. If you get botulism, tetanus, rabies, or a venomous snake bite, you hope and pray that antitoxin is available nearby. These situations are otherwise almost impossible to survive.

Antibodies can also save lives by recognizing cancer cells and flagging them for destruction by the immune system. Conjugated monoclonal antibodies are used to deliver a “payload” of chemotherapy drug. By either route, the bad cells can be eradicated without harming innocent bystanders, which has always been the loftiest goal of oncologists. There are over 100 mAb therapies FDA-approved for use in humans, and the number is expanding rapidly. In our next piece, find out about the mAbs made exclusively for dogs and cats.

Dr M.S. Regan