Lilly asked what happen when the pathogen makes it passed the first shields, "well" her said mother that's when active proteins come in and warn all the good cells that theirs a pathogen. by warning them white blood cells know that they have to do their job.
The white blood cells go and try to get rid of the pathogen. There basically the hero all of this.
They all work together to help you !
Sometimes pathogens have antigens on them, antigens are an ID protein which alerts the body when the pathogen is in. The white blood cell engulfs the pathogen and presents the antigen through its membrane.
After WBC engulfs the pathogen , the helper T cell comes and his job is to read and copy the antigen. "whats next" Lilly says eagerly. "Well after that theirs two pathways it can go the hum moral pathway or the cell mediated pathway", says the mother.
The humoral pathway involves the B cell. which prevents anymore infections. It sends all the information that the helper T cell gives and send the information to the plasma cell and there the plasma cell makes antibodies.
Once the plasma cell makes antibodies, it gives the antibodies to the memory B cell where it makes immunity , so next time you get sick it will prevent you from getting sick.