mom my throat hurts! How did this virus get in my body anyways?
you can also get sick on a dusty day since pathogens are in the dust you breathe
Well honey there are many different ways a pathogen can enter your body...
For example, you could be talking to someone, but suddenly they sneeze, and that bacteria from their sneeze floats throughout the air and enter your body through your eyes, nose, or mouth!
that's why you should always stay home or go see a doctor so you don't get other people sick
In your case, your second line defense system thought it was best to make your temperature higher since pathogens don't do so well under heat, but instead this only made you feel worse and kill only some of the pathogens. Therefore, the immune system calls for backup.
Although, our body has many defense mechanisms that try to keep the pathogens away from your body. For example, when your sweating under the sun, that sweat kills pathogens who come onto you skin.
Usually, something called an antigen is what triggers the immune system response. At that point, cells that are known as antibodies (production of protein) try and kill the antigens, and they wouldn't kill the good cells since they have something called a binding site which allows them to "ignore" the good cells and destroy the bad ones
Mom if the sweat and other defense mechanisms were supposed to keep the virus out of my body, then how did I still get sick?
Sometimes, the first line defense mechanism fails and that's where the second line of defense comes in.