How severe viral infections overwhelm immune cells

When it comes to fighting viruses and cancers, our bodies rely on a type of white blood cell called Killer T cells that recognise and eliminate infected cells, effectively stopping the infection or tumour from progressing.

While T cells are tremendously efficient infection fighters; they can’t keep fighting forever. So at some point they effectively turn off in a process termed ‘immune exhaustion’. This involves the cells expressing high levels of so-called immune ‘checkpoints’, including a receptor called PD-1, which limit the further activation of T cells.