Dr. Joseph Mikhael: To better understand immunotherapy, let's quickly review the basics of the immune system. Our immune system is complex. It works in many ways, and there are many parts of the immune system, which includes several organs and connections between them. To keep it simple, let's think about two important parts of the immune system, cellular immunity and humoral or antibody immunity.
Cellular immunity. Our immune system has many types of cells that protect us. Two very important cells to our discussion today are natural killer cells, sometimes called NK cells, and T cells. These are highly specialized cells that can be trained to react to things that could potentially hurt the body and destroy them. Think of them like soldier cells. Natural killer cells or NK cells are your body's first line of defense. NK cells search your body looking for infected or cancerous cells, and when they find them, they kill them to slow the spread of that cancer or infection.
T cells have a somewhat similar role to natural killer cells, but they're more specific. They recognize a particular cancer by something on the surface of that cancer or a particular type of infection.
Humoral or antibody immunity. This is one of the most important parts of our immune system and it creates antibodies that can protect the body. Plasma cells are the cells that live in our bone marrow and make antibodies. Ironically, these are the same cells that become cancerous in multiple myeloma. So when we are exposed to something that can harm us or when we've been given a vaccination, plasma cells respond by making antibodies to recognize that specific threat. In fact, they have a unique Y shape that allows them to hook onto that enemy cell, and when they hook onto that enemy cell, they hook onto what we call an antigen or something that sticks out of the surface of that cell. The back part of the Y will then cause the immune system to respond to destroy that enemy. Once they have attached to the cell, they can trigger the whole immune system to respond and destroy that cell.
When we engage this complicated machinery of a patient's own immune system to target or kill cancer cells, we call this immunotherapy.