In the Real World
Research and Animal Systems
Many years ago scientists realized that the same antibodies produced by B cells that normally fight off a cold could advance medical research. So they set off to design and produce antibodies that sought out particular proteins in the body (perhaps some that were a part of a neuronal receptor).
Making antibodies is complicated and time consuming, so we aren't going to belabor the details here. Just to give you the basics, research antibodies are made by "immunizing" an animal with a particular antigen. Scientists inject the antigen into a lab mouse, and its own immune system launches an attack. The mouse's B cells make lots of antibodies that react to that particular antigen. Scientists can then snag those antibodies, isolating them from the rest of the stuff inside a mouse, and add them to a piece of bodily tissue. These newly synthesized antibodies then bind to that particular protein the scientists had in mind.
In the lab, scientists use antibodies in a technique called immunohistochemistry to visualize particular proteins. Each antibody is developed to recognize a particular protein, and when these same antibodies are attached to a fluorescent tag, scientists can see where the protein hangs out in a particular tissue—just look for the glowing parts. Essentially, when the fluorescent tags are excited with specific wavelengths of light, they glow.
Scientists have been able to take some amazing pictures of the body this way. But not only do these pictures look totally awesome, this immunohistochemistry technique has expanded our knowledge of how the body works.
The cool part about all of this is how research has used antibodies to help treat diseases. Take cancer for example. Chemotherapy, a common type of cancer treatment, has all sorts of nasty side effects. Patients lose their hair, they lose weight, and their immune system suffers because the treatment hits all cells, both cancerous and not. The idea is that if researchers are able to locate particular cancer cells, cancer therapy could be more direct, and a patient would experience fewer side effects as we reduce the number of healthy cells caught in the chemo crossfire.
Different types of cancer cells express different types of surface proteins and/or antigens, so researchers use this characteristic to their advantage to create antibodies that recognized a specific cancer cell antigen. When they inject these antibodies into animals, the antibodies seek out the cancer cells and destroy them. To provide cancer therapy, scientists use these antibodies in different ways.
First, they let the antibodies point out the cancer cell to the patient's immune system, and let it attack those cells specifically. It took years to develop this technique, but it is extremely useful in treating lymphoma. Because lymphomas come from B cells, and all B cells express a particular protein called CD20, the antibodies target both healthy and non-healthy B cells. Once they "tag" these cells, the patient's own immune system can kick in to destroy all B cells.
Since cancerous cells grow like crazy, blocking their ability to grow is another way to specifically fight those cells. Cancer cells express lots of growth factors and secrete growth signals to blood vessels to keep growing. Antibodies that are specifically on the lookout for these growth signals can help prevent the cancerous cells from growing, and cut off the cell's blood supply. Researchers used this technique to develop drugs that target different types of cancers, including colon cancer.
A more specific way to directly attack cancer cells is by attaching radioactive drugs to the antibody. So not only is the antibody hunting down cancer cells to call in reinforcements, but it's packing heat as well. Essentially, the antibody-tagged cancer cell receives a small dose of radiation for as long as the antibody remains attached. Since the antibody is attaching to cancer cells in particular, the radioactive particles are only bound to cancerous cells (and leave the healthy ones alone), which means the side effects from radiation are less severe. This is how a drug that's used to treat non-Hodgkin's lymphoma works.
Antibodies have helped scientists treat other diseases too. They've been approved, in various forms, to treat cardiovascular diseases, transplant rejection, and multiple sclerosis. It's amazing what we've been able to get these antibodies to do.
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