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University of Basel

Control of cell population sizes: When is enough enough?

Illustration: T cells interact due to their high density
If the upper threshold density of T cells is reached, cell death is initiated. (Image: Biozentrum, University of Basel)

Researchers at the University of Basel have uncovered a cell-intrinsic mechanism that controls the appropriate number of T cells in the organism and thus ensures that the immune system functions properly. This mechanism has also been found in slime molds, suggesting that this regulation of cell density is evolutionarily conserved.

09 November 2022 | Heike Sacher

Illustration: T cells interact due to their high density
If the upper threshold density of T cells is reached, cell death is initiated. (Image: Biozentrum, University of Basel)

Our immune system, which is responsible for controlling attacks from viruses, bacteria, parasites, but also preventing the occurrence of cancer cells, consists of multiple cell types. There are billions of these immune cells in our body, including T lymphocytes, or T cells for short. T cells are produced in the bone marrow, selected in the thymus and are essential for a proper functioning of our immune system. While enough T cells need to be present at any time, the body must also ensure that they do not exceed a certain density. But how does the immune system recognize whether the correct number of T cells are present within the circulation?

Coronin proteins control T cell population size

The research team led by Prof. Dr. Jean Pieters at the Biozentrum of the University of Basel has now been able to uncover the cell's own mechanism that regulates the population size of T cells. Their previous work, as well as that of other groups, already showed that a protein called coronin 1 plays an important role in the survival of T cells in the body.

In the new work, the researchers report that when the numbers of T cells rise, the expression of the protein coronin 1, that is already among the most abundant proteins in T cells, is further increased. This promotes the survival of the T cells and thus ensures a sufficient size of their population.

Video: T cells require the protein coronin 1 to reach and maintain their cell population size. The movie illustrates T cells dividing until their appropriate density has been reached, after which coronin 1 production reaches a plateau. As a result cell death (cells turning red) is initiated and T cells begin to die until the appropriate density has been reached again. (Source: Group Jean Pieters, Biozentrum; Animations: New Medium Center, University of Basel)

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