Immunity: rapidly responding T cells (Introduction)

by David Turell , Monday, July 16, 2018, 21:26 (2111 days ago) @ David Turell

Surface receptors on the T cell surfaces are widely dispersed to quickly pick up signals from foreign antigens:

https://www.sciencedaily.com/releases/2018/07/180716114610.htm

"Without T cells, we could not survive. They are a key component of our immune system and have highly sensitive receptors on their surface that can detect pathogens. The exact way that these receptors are distributed over the surface of the T cells is still not completely understood, but the analyses by TU Wien show that previous ideas are no longer tenable.

"It was previously thought that the T cell would concentrate the receptors at certain points in order to achieve the highest possible sensitivity. As a current publication by the biophysics research group at TU Wien shows, T cells are actually programmed to react as quickly as possible, and therefore their receptors are arranged at random.

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"'A T cell is a highly specific molecule detector," explains Prof. Gerhard Schütz, head of the biophysics research group at the Institute of Applied Physics at TU Wien. "Each T cell only reacts to a very specific molecule, and so we need many different T cells in our bodies." Each T cell carries many thousands of copies of the same receptor on its surface.

"To trigger an immune reaction, the T cell still needs an important partner -- the so-called antigen-presenting cell. The surfaces of these cells present many different molecules with the aid of special carrier proteins. Some of these molecules originate from endogenous structures and are harmless, but characteristic antigens of harmful intruders are also transported by the body on these antigen-presenting cells.

"If the T cell comes into contact with one of these antigen-presenting cells, the search for a needle in a haystack begins. What happens if a molecule of the exact type for which the T cell is programmed, is found amongst the many hundreds of thousands of molecules that are on the surface of the antigen-presenting cell? "Imagine that the T cell has countless versions of the same key on its surface, and now has to quickly find out whether it fits any of the hundreds of thousands of locks on the antigen-presenting cell," explains Gerhard Schütz.

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"The receptors might well be distributed randomly over the T cell. That would also explain why the immune reaction happens so quickly. Regardless of how the antigen-presenting cell comes into contact with the T cell, the T cell always has a 'key' that fits the 'lock' at this location. If this is correct, the two cells do not lose any time getting into the right position, but instead the immune reaction can be triggered immediately.

Comment: The T cells develop a library of antigen receptors to protect us. This had to be designed early in evolution for life to survive infections. The information is developed and stored in the thymus where T cells are made.