But how did inoculation generate immunity, particularly long-term immunity? Some factor produced in the body must be able to counter the infection and also retain a memory of the infection over multiple years. Vaccination, as we will soon learn, generally works by inciting specific antibodies against a microbe. The antibodies come from B cells, and they are retained in the cellular memory of the host because some of these cells live for decades—long after the initial inoculum was introduced. We will turn to how B cells manage to achieve memory, and how T cells help, in the next chapter.
