Crash Course
Your Immune System: Natural Born Killer - Crash Course Biology
Hank tells us about the team of deadly ninja assassins that is tasked with protecting our bodies from all the bad guys that want to kill us - also known as our immune system.
Cells Alive
Cells Alive!: The Cytotoxic T Lymphocyte
Nice graphic of the T-lymphocyte in action. Click on the "640K movie" link for a Quicktime movie of the cell killing an influenza virus. Some of the animations are offered for sale, but some are available free.