By Mark A. Kelley, MD |06/20/16
Humans have been fighting disease for thousands of years. Until the 20th century, most people died young because they were exposed to deadly infections like small pox. However, smallpox survivors never experienced the disease again. The same is true for mumps, polio and measles. During these infections, our bodies create antibodies that recognize the virus as an alien invader and kill it before it can infect again. We have used this immune system to prevent infections and now we are using it against cancer.
The war against infections has been so effective that some infections are now rare. In fact, smallpox has been eradicated across the world. The reason is that we have developed vaccines that expose the body to proteins from viruses (like small pox) or bacteria (like tetanus) These proteins cause no infection but stimulate the body’s immune system to create antibodies that kill these organisms. Vaccines are among the most important discoveries in history and have saved millions of lives.
There are a few twists to this story. First, our immune system may need a “wake-up” call with a booster shot of vaccine. This revs up the immune system to create a fresh reserve of antibodies. A good example is the tetanus booster shot.
Second, viruses can change their appearance over time so that the immune system may not recognize them. For example, the influenza virus can change every year. Therefore, we need an annual flu shot to keep our immune system up-to-date.
In the past year, two different viruses, Zika and Ebola, have caused major epidemics. The Ebola virus is easily passed from human to human and has a high mortality rate. The Zika virus is transmitted by mosquito bites and rarely causes death or serious illness. The exception is unborn infants. For them, Zika can cause severe brain destruction leaving them disabled for life.
Both these viruses began in remote tropical areas of Africa and would have gone unnoticed before modern times. However, with larger cities and modern travel, diseases can rapidly infect people around the globe. Ebola, for now, has been confined to Africa, but Zika is steadily spreading across the Western Hemisphere.
These epidemics have awakened the world to the value of vaccines. There are now major efforts to create vaccines for these two dangerous viruses. However, it will take time to be certain that any new vaccine is safe and effective
The immune system is also becoming important in treating another major disease—cancer. Some cancers are linked to a viral infection. The best example is cervical cancer, which is associated with infection by the human papilloma virus. Vaccines against that virus, when given before puberty, reduces the risk of cervical cancer.
Cancer is a collection of abnormal cells that grow uncontrollably. Our immune system does not kill these cells because, on the surface, they look normal. If we could make these cells look abnormal, the immune system would destroy them quickly, just like any other invader. The effect would be dramatic. The immune system patrols the entire body and would hunt down every “strange” cancer cell.
Cancer research is now probing how to use our immune system to cure cancer. One approach is to make the cancer look like a foreign invader to our immune system. Another is to teach our immune system to use antibodies engineered to sabotage the growth of the cancer.
It may be a long time before we see results from this research … but we should be patient. It took decades to develop vaccines but the results have been spectacular. Our immune system is smart and ruthless in protecting us from infection. If we can train it to fight cancer, we will be moving closer to a cure.