What happens to a
pathogen that has been flagged by an antibody?

The antibody does a couple of things; it’ll interfere with the pathogen’s movement. Think of it like a kid that is holding onto their parent’s legs. Said parent will slow down even more if more kids (antibodies) latch onto them. It’ll also act as a little flag for phagocytes, signaling that whatever they’re latched onto is something to eat. I hope this is enough to help out!