Here's a well done short animation that explains how the human immune system works in the face of a bacterial infection. A very informative Youtube video series created by Kurzgesagt.
"The immune system is a powerful army of cells that fights like a T-Rex on speed and sacrifices itself for your survival. Without it you would die in no time. This sounds simple but the reality is complex, beautiful and just awesome." - Kurzgesagt
It's a jam packed 7 minute video CLICK HERE TO WATCH