I can’t embed the video on this post, but a short video presentation on how the immune system works is worth looking at. Great mix of brief text explanations combined with actual footage of immune cells doing their thing in the body: gobbling up bacteria. Just click on one of the two presentations then click/drag your way through it.
It’s kind of neat how these captured, moving images of immune cells show that this stuff is real, not just theoretical. Kind of reminds me of that movie Fantastic Voyage from like 50 years ago. And I do have footage of that. Attack of the white blood cells!