All medical research is carefully planned, and this includes medical
research with animals. Experts who review a scientist’s proposed
experiment involving animals weigh several considerations before
approving each study.
The most important thing is that the research must be relevant
to human or animal health. Studies need to protect the animals’
welfare. That means that only the fewest number of the most
appropriate species may be used. Under federal law, all animals
must be treated humanely and undergo the least distress possible
I'm guessing you mean it in this regard: They use animal testing with things like vaccines and cures. Say they give a rat the ebola virus - they test on them to see which cures or vaccines work, or which could possibly cause death just so they can save us humans.
After the macrophage fails the Helper T Cell stimulates the B cells if pathogen is extracellular and Cytotoxic T Cells if the pathogen is intracellular. Once the pathogen is killed the B Cells create Memory B Cells and the Killer T Cells create memory T Cells.
