Immunity system complexity: T cell differentiating daughters (Introduction)

by David Turell , Friday, May 20, 2022, 22:51 (706 days ago) @ David Turell

One new T cell remembers en emies , the other fights them::

https://medicalxpress.com/news/2022-05-killer-memory-dna-isnt-destiny.html

"The researchers showed how a specific protein complex guides translation of an important immune transcription factor in one region of the parent T cell. When the cell divides, because the transcription factor is only in one region, it is then inherited asymmetrically into two daughter cells. The transcription factor drives expression of a set of genes in one daughter cell, pushing it to become an effector cell, while the other becomes a memory cell.

"'Our results hint that events that happen very early in a T cell's life can influence the function of the cell much later," said corresponding author Doug Green, Ph.D., St. Jude Department of Immunology chair. "We have uncovered one way in which the immune system ensures that when T cells are activated, the response will be diverse, with some cells, the effectors, launching a rapid assault on the invader and others hanging back in reserve for later, as memory cells."

"The immune system has many different cell types with varied functions. One major cell type is CD8+ T cells. These cells are responsible for directly killing infected and tumor cells. They are activated by a special cell that presents a bit of virus or tumor cell, called an antigen, on their surface. The point of contact between T cells and the antigen-presenting cells is called the immune synapse. After activation, the T cells divide into genetically identical daughter cells.

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"...the researchers discovered that the protein complex that makes c-Myc was only present near the immune synapse. The specific complex responsible for translating c-Myc is called the eukaryotic translation initiation factor 4F (eIF4F) complex. The eIF4F complex is translation machinery, which takes mRNA messages and makes them into proteins, in this case, c-Myc.

"The c-myc mRNA has a complicated structure on one end. Only the eIF4F complex can use the complicated structure of the c-myc mRNA to start the translation process into protein. Therefore, c-Myc is only produced where eIF4F is present, which relegates c-Myc to one side of the cell.

"This is the first time that the location of translation machinery has been described as the reason why a protein is present in only one part of the cell.

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"'This study is the first time that we could say, with confidence, that two sister cells can have very different gene expression patterns," Green said. "The study also demonstrates that there are basic principles of cellular architecture, which create platforms on which intracellular events can localize. Upon division, asymmetries in the distribution of these platforms can result in diversification of cell fate. The details may not be the same for other cell types, but the principles are likely to hold.'"

Comment: a cleaver solution, since T cells must attack antigens, but also need memory of past attacks to be fully prepared for new ones. Like all T-cell functions, this had to be designed to protect organisms from the beginning of tbeir origin in evolution.