What does the human immune system produce that is the basis for immunization?

The immune system produces any cells that can protect us from foreign Invaders and leave the healthy ones alone. White blood cells, dendritic cells, macrophages, special proteins for immune purposes. The basis of immunization is basically to inject the patient with an inactive pathogen so that way the patient's immune system can at least have some experience with the pathogen and come up with a game plan.