Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: When a person is infected with the influenza virus, the immune system defends the body through a cell-mediated immune response. Which immune cell is responsible for protecting the body from the influenza virus infection?
CD8+ T cell.