Answer:
Sometimes a person’s immune system does not work properly. This can result from immune deficiencies present at birth; medications that suppress the immune system, like steroids; unnecessary or overzealous immune responses, such as allergies; or immune responses to one’s self, called autoimmunity. One of the amazing aspects of the immune system is that it is compensatory, meaning that when one part is weak or non-functional, typically another part can step in. Think of it like a trip to the grocery store. If you need to go to the store, but your tire is flat, you may go by another method of transportation — another motor vehicle, a bicycle or walking. The substitute may or may not be as efficient, but it still allows you to complete your task. The same is true of the cells and proteins of our immune system; most “jobs” of the immune system can be done by more than one part of the immune system although some parts are better at certain jobs than others.
This same feature that makes the immune system flexible also makes it difficult to study. This is why studies in the lab, and even in animals, still need to be repeated in people before we can be sure the findings apply. However, laboratory and animal studies remain important because they provide us with preliminary information that puts us in the best position to succeed when we complete studies in people.
All of this said, sometimes people still have conditions that alter their ability to respond to infections, so let’s take a look at a few and explore how the immune system works in these unique situations
