T cells: YouTube video with pdf summary sheet

This is a pdf summary sheet with a linked YouTube video. It summarises the role of two important kinds of T cell: helper T cells and Killer T cells. The sheet has a link and QR code so students can access the video version of this resource.

Description of the YouTube video:
T-cells play a central role in our response to infections. They act in two different ways, summarised in this video.

There is one strategy for identifying cells that have become infected or are abnormal. These are the Killer or cytotoxic T cells. These cells recognise infected cells through receptor molecules called T-cell receptors. What they recognise are short pieces of foreign antigen presented a bit like a picture in a frame on a presentation molecule called MHC class I on the surface of the infected cell. The MHC class I act like windows to the inside of the cell, whilst at the same time acting as a mark of quality to other cells. They say: “this is good quality information”

Pieces of pathogen that have been eaten by immune cells like macrophages are presented to a different kind of T-cell, called a T helper cell. This distinction is important because it would not be helpful for killer T cells to start killing cells that are doing a good job in eating pathogens. Instead the role of the T helper cell is to stimulate other immune cells such as B cells. B cells are instructed by T helper cells to make more antibodies. They are in effect saying to the B cell “great job-keep doing what you are doing!”. The way T helper cells recognise macrophages that have eaten pathogens is again through their T cell receptors. However, the T cell receptors of T helper cells recognise pieces of foreign antigen that are presented on MHC class II molecules, again a bit like a picture in a very specific frame that tells the the T cells that this is reliable information.