Cytotoxic T lymphocytes are an important component of cellular immunity. These T cells are responsible for hunting down other cells of the body that are infected by viruses and destroying them. That is why they are called "cytotoxic" - they are killers of cells. Many vaccines work, at least in part, by stimulating this type of t cell activation, or response.
Viruses cannot reproduce on their own. They need to take advantage of the replication machinery that is present in the cells of the creatures they infect. Fortunately, the human immune system has developed a way to use this fact to its advantage. When viruses are using a cell to reproduce, the cell "displays" some of the viral proteins on its surface. Cytotoxic T cells can recognize these components and hone in to destroy the infected cells before they can release the new virus into the bloodstream. Cytotoxic T cells also create chemicals known as cytokines, which help coordinate how the immune system fights against disease.
Cytotoxic T cells are specific for a particular type of virus, and once a cytotoxic T cell response has been initiated against a particular virus, it becomes an important component of viral immunity. However, large numbers of these cells don't lurk around all the time. When there's no infection, they're simply not needed. This is where memory T cell function becomes important.
Memory cells literally remember the specialized cells that the immune system produced in order to fight a previous infection (or that were made after a vaccine challenge.) When a new infection occurs, the memory T cell goes into action and produces a large number of cytotoxic T cells at a very fast rate. This is much quicker than developing a new response to a pathogen. Memory cells are also important in mounting a strong and fast antibody response after vaccination or initial infection.
Did You Know: Lymphocyte is the general name for the white blood cells that are made in the immune system
