By Ross Keller, PhD candidate in Biomedical Science.
What is the immune system?
The human body is continuously under assault from a wide array of things that would do it harm. Many of these come in the form of pathogens—or microbes that infect the body and are not part of the body’s flora. These microbes range from common cold viruses to pneumococcal bacteria to deadly viruses like Ebola.
However, the body can also come under attack from itself in a number of ways. One manner this occurs is when normal cells transform and begin dividing uncontrollably. Over time the rogue cells begin invading organs and destroying their normal function—this is known as cancer.
But, the human body has been evolving for millions of years, and over that time it has developed an extensive and complex defense system to ward off outside invaders like pneumonia as well as home-grown usurpers like cancer. It is termed the immune system.
The immune system is a complex network of non-specialized and specialized cells that each have a role in keeping the body safe. It can be divided into two broad categories: innate and adaptive. The innate immune system is the body’s way of attacking pathogens in a generic way, meaning many types of invaders will be treated equally—it acts fast. On the other hand, the adaptive immune system is composed of specialized cells that remember the specific type of invader and mount a specific attack when the invader is encountered a second time—it acts slowly the first time and quickly the second.