If your immune system cannot do its job, the results can be serious.

They may have already had another problem with their immune systems.

They usually have no effect on us because our immune systems deal with them.

For the last 18 months he has had no immune system to speak of.

They are now considered to be part of the immune system.

The body has its own defense against disease called the immune system.

Others might increase the activity of the body's immune system.

They help to control the immune system and fight disease.

Their immune system did not learn how to fight it well.

The body's ability to fight off a disease is called its immune system.