The Immune System

In this topic, you learned the steps your immune system takes to protect your body against pathogens. When a pathogen enters your body, your white blood cells produce antibodies against it. If the same type of pathogen returns, your white blood cells remember it and are able to respond quickly before it invades your cells and tissues. This process provides you with immunity.

Sometimes pathogens have hundreds of variations, such as the flu virus. Your body does not have antibodies for every type of flu virus, making it possible for you to get the flu more than once in your life.