Blood = cells + plasma ex. antibodies, serological tests. Through breast feeding, when baby drinks milk, he gets a lot of antibodies that will protect the babies gastrointestinal tract from different pathogens, thus if you are breastfeeding, less gastrointestinal infections) Passive also links to artificial which links to antibodies from someone else which links to used as a drug. Can be antibodies from another person or animal. Isolating antibodies from one person, and injecting into a person who needs immediate care. Animals sometimes have antibodies that humans may not have because they were not supposed to be exposed to that antigen in the first place. Used for treatment of cancer or tumours. Specific type of antibodies can stop lung cancer which are mediated by over activation of receptors. Bind to target cells of tumour cells which stimulate person"s immune system to attack those cells. Passive immunity is really used as a drug.