To find an answer to this question, researchers Kaspar Bresser and Lianne Kok developed a tool to measure how often the T cells had divided. They already knew that mutations – errors in the DNA – could occur during each division. They could use these errors to measure the number of times the cells had divided. So they put an artificial piece of DNA – one that is very sensitive to errors – into the T cells. Once an error occurred in this piece of DNA, the cell and all its descendants turn red. “The higher the number of red cells in a population, the more divisions have occurred,” Bresser explains.
This error recorder, named DivisionRecorder, is the first of its kind. It can track hundreds of cells instead of the 5 to 8 divisions that our more conventional methods are able to track.
The researchers also found that a second infection with the same pathogen caused these young memory T cells to divide rapidly in order to fight the infection. Bresser: “This is the first proof that shows that T cells that have not divided often are crucial in the prevention of a reinfection.”
The researchers state that this study underlines the importance of young memory T cells that they have identified as the cells that you want to trigger through inoculation. “These young memory T cells are very fit and powerful during reinfection. By gaining a better understanding of what these cells look like and how they work, we could potentially improve our vaccines and have a better understanding of when booster shots should be provided,” Ferenc Scheeren states.
But there are other applications for this fundamental discovery that are currently being considered, including ones concerning cancer immunology, on which researchers from the Netherlands Cancer Institute are collaborating. Bresser: “What we are all searching for is the most powerful and best functioning T cell, which could be beneficial for immunotherapies against cancer. We are looking through numerous data sets. The characteristics of ‘our’ memory cells could be a new lead in this search. That’s why we want to understand these T cells through and through.”