2022-01-10 15:12:47
The saga dedicated to learning about the immune system in conversations with Jorge Laborda is revealing the marvelous complexity of our defense system against infections. Throughout the nine previous chapters that you can listen to here: [1], [2], [3], [4], [5], [6], [7], [8] y [9], Jorge Laborda has been presenting, step by step, the different actors that make up this great army of cells and molecules that defend us from the invasions of viruses, bacteria, fungi and substances of various kinds. Today it is the turn, once again, of the T lymphocytes, an elite body belonging to the adaptive immune system that reacts by developing weapons and strategies against a specific enemy that has already opened a breach in the defenses and is infecting the organism.
In conventional wars, when an invasion occurs, the battlefield takes place within one’s own territory, where, unfortunately, attackers and attacked are mixed without a defined line separating them. In these circumstances, a mass attack can be very damaging to one’s own forces, because they would suffer the collateral effects of the attack. Thus, any strategy requires knowing exactly one’s own in order to avoid damage from “friendly fire”.
In the generation of the elite forces of the immune system, the T lymphocytes learn to differentiate their own in the first place, in this way everything that is not recognized as their own will belong to the enemy and its detection will trigger a series of reactions aimed at using an arsenal of weapons against him.
Now, how does this recognition come about?
Our cells communicate with the external environment through their membranes, on this external border they place some molecules that have been collected from the interior of the cell and that uniquely identify them. These proteins are produced by the genes of what is known as the “major histocompatibility complex”, known as MHCfor its acronym in English.
There are two main classes of these genes, which are called MHC of type 1 (MHC-1) y MHC of type 2 (MHC-2), which fulfill different missions.
the genes of MHC-1 are responsible for generating proteins that place pieces (peptides) of molecules that exist inside the cell on the cell surface. Logically, a healthy cell will only expose peptides from its own activity, in other words, these proteins will be a kind of identity card that identifies it. If this healthy cell were to meet a T lymphocyte, it would detect it as a “friend” and nothing would happen. Now, if the cell is infected by a virus, it will have taken over the cellular machinery for its own benefit and the cell will begin to manufacture virus proteins. These proteins, being inside the cell, are also presented in the membrane. In this case, the T lymphocyte that detects them will identify them as foreign and will activate, sending a signal for the infected cell to commit suicide before generating more virus.
But not all cells that have foreign proteins on the membrane are infected. We know that there are cells of the immune system, such as phagocytes, whose task is to engulf bacteria, viruses and foreign particles and destroy them. The remains of the destroyed enemy also generate molecules that the second type of major histocompatibility complex genes (MHC-2) will present on the cell surface. In this case, the encounter with a T lymphocyte will also cause its activation, but with very different effects. Instead of sending a suicide signal to the cell, which would be counterproductive because that cell is healthy and only presents the enemy’s peptides as a consequence of its activity, the T lymphocyte will undergo changes aimed at enhancing the activity of phagocytes and other cells of the innate immune system to reinforce their attack against the enemy.
Cells are blind and deaf, they can only meet other cells by contact with each other, which is why Jorge Laborda tells us a story that allows us to understand how they differentiate friends from enemies: The story of the tribe of “carasbuenas”. This fictional tribe, made up of blind and deaf people, has to defend himself against the attack of another tribe and idea and develops a strategy that allows him to identify friends by making masks that do not exactly fit the faces of the members of the group. tribe but that can knock out those enemies in which the adjustment is complete. I invite you to listen to the story in this new installment of the Hablando con Científicos podcast.
Jorge Laborda is Professor of Biochemistry and Molecular Biology at the Faculty of Pharmacy of the University of Castilla-La Mancha. (Albacete) and author of the Quilo de Ciencia Podcast.
CHAPTERS ISSUED
We are surrounded! immune system 1.
The chemical warfare of the Immune System 2.
Alarm, we are attacked! Immune system 3
Adapting to the enemy within. immune system 4.
Reporting on the enemy. immune system 5.
B lymphocytes and antibodies. immune system 6
Antibody test and T lymphocytes. Immune System 7
Licensed T cell to kill or collaborate. Immune system 8.
A different weapon for each lymphocyte. Immune system 9.
BOOKS:
Your defenses against coronavirus. A brief introduction to the immune system
Your defenses against coronavirus. A brief introduction to the immune system.
Your defenses against coronavirus. A brief introduction to the immune system.
Deflamed immunology: An introduction to the immune system and its pathologies
Deflamed immunology: An introduction to the immune system and its pathologies
Deflamed immunology: An introduction to the immune system and its pathologies
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