How do you control the number of cells in an organism?

Researchers at the University of Basel have discovered an intrinsic cellular mechanism that controls the right number of T cells in the body to ensure the immune system functions
properly.
This mechanism has also been found in slime molds, suggesting that this regulation of cell density is evolutionarily conserved
.

Our immune system is made up of a variety of cells that control the attack of viruses, bacteria, and parasites, while also preventing cancer cells from occurring
.
We have billions of these immune cells in our bodies, including T lymphocytes, or T cells
for short.
T cells are produced in the bone marrow and selected in the thymus gland, which are essential for
the proper functioning of our immune system.
While enough T cells need to be present at all times, the body must also ensure that they do not exceed a certain density
.
But how does the immune system recognize if the number of T cells in circulation is correct?

Coronary proteins control the number of T cells

The research team, led by Dr.
Jean Pieters, professor at the University of Basel's Centre for Biology, has now been able to discover the mechanism
by which this cell itself regulates the number of T cells.
Their previous work, as well as that of other groups, has shown that a protein called coronin 1 plays an important role
in the survival of T cells in the body.

In the new study, the researchers report that when the number of T cells increases, the expression of coronavirus protein 1, already one of the most abundant proteins in T cells, increases
further.
This promotes the survival of T cells, thus guaranteeing a sufficient number
.

But how does the system decide when enough is enough? The researchers found that when the T cell density reached its upper limit, coronavirus protein 1 production stopped
.
As a result, cell survival signals triggered by coronary protein 1 disappeared
.

"The cells start to die and the density of T cells decreases again," explains
Tohnyui Ndinyanka Fabrice, first author of the study.
"It took a long time
to visualize the process.
But once obtained, our observations are like watching a disaster movie: if cells are overcrowded, mass death within clusters of cells begins
.
”

An evolutionarily conservative mechanism

Interestingly, the results also showed that coronary protein regulation
of cell numbers was also found in amoeba (slime molds) that go through single- and multicellular stages.
This discovery opens up exciting avenues
for future research.
"Coronavirus family members are highly conserved and widely expressed in the eukaryotic kingdom," said Professor Jean Pieters
.
"Future work may clarify whether coronavirus-dependent regulation of corresponding T cells and slime flora is applicable to other systems
as well.
"