 Hello, my name is John Nettle and I teach human biology, anatomy, and physiology at Shasta College. In this video, I will explain how the immune system works, specifically I will focus on how does the human body develop immunity to COVID-19. This video is intended to help you understand the importance of inflammation, antibodies, and white blood cells. If you would like to learn more, I've created several videos on my YouTube channel that go into more details about the structure and function of the immune system. When a person becomes immune to a disease caused by a virus like COVID-19, their immune system produces a memory of that virus. However, it takes time for the immune system to develop this memory after being exposed to a new virus. COVID-19 is the disease caused by infection with the novel coronavirus known as SARS-CoV-2. Here is an illustration of the virus. The genetic instructions of this virus are made of a molecule called RNA. And the outer layer of the virus surrounding the RNA is an envelope containing several other molecules that are important for allowing the virus to infect our cells, including the spike protein. I emphasize this molecule, the spike protein, because it also functions as an important marker known as an antigen that the immune system uses to recognize the virus. An antigen is a molecule that the immune system uses to form a memory of a specific infection. Although there are other coronaviruses that infect humans, the spike protein of the novel coronavirus has a different shape than the spike proteins of other coronaviruses. So our immune systems are not prepared to defend against this new virus. When the virus gets in our body, the spike protein tricks our cells into letting the virus inside. Once inside of our cells, the virus can make copies of itself and wreak havoc on our bodies as it continues to spread. Inflammation, antibodies, and white blood cells are the major tools that the immune system will use to defend against this infection. You may be familiar with the major signs of inflammation which are redness, swelling, heat, and pain. Inflammation occurs when the immune system recognizes an infection. Although it can make us uncomfortable, inflammation is the body's way of sending in white blood cells and antibodies to stop the virus. Antibodies are proteins produced by a specific type of white blood cell known as a B cell. Antibodies defend against the coronavirus by binding to the spike protein. These antibodies neutralize the virus, blocking the spike protein so that the virus cannot enter our cells. There are many different types of white blood cells in the human body. Another type of white blood cell known as a cytotoxic T cell also helps to defend against the virus by destroying cells that have already become infected. While antibodies protect against the virus by neutralizing viruses to prevent them from infecting our cells, cytotoxic T cells work to destroy cells that have already become infected in order to prevent the virus from making copies of itself. While the immune system can develop defenses to protect against this novel coronavirus, the process takes several weeks to develop immunity after you've been exposed to the virus. Unfortunately, this virus is highly contagious and some people are unable to fight off the infection. In fact, more than 300,000 people died from COVID-19 in the United States during 2020 alone. Globally, more than 1.8 million people died from COVID-19. Vaccines allow the immune system to prepare defenses against the novel coronavirus so that we can become immune to COVID-19 without the risk of being exposed to the virus. While testing, social distancing, masks, and hygiene remain important strategies to slow the spread, vaccination is the safest pathway to immunity. Thank you for watching this video.