Immunity: detecting dangerous bacteria (Introduction)

by David Turell , Thursday, November 16, 2017, 19:33 (2565 days ago) @ David Turell

Cells have a complex way of detecting bad bacteria. Since bacteria came first, when multicellular forms arrived on the scene, they had to have this mechanism in place to survive:

https://medicalxpress.com/news/2017-11-immune-invading-bacteria.html

"The body's homeland security unit is more thorough than any airport checkpoint. For the first time, scientists have witnessed a mouse immune system protein frisking a snippet of an invading bacterium. The inspection is far more extensive than researchers imagined: the immune system protein, similar to those in humans, scans the bacterial protein in six different ways, ensuring correct identification.

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"'The immune system protein uses many protein parts, including some of previously unknown function."

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"HHMI Investigator Russell Vance had been studying the NLR superfamily of immune system proteins, which plants and animals use to detect pathogens that have slipped inside cells. He wanted to see one such protein, called NAIP5, as it inspected bits of protein shed by the disease-causing bacterium Legionella pneumophila. Earlier genetic studies had identified NAIP5 as an important player in host resistance to Legionella, and Vance's team wanted to take a closer look.

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"The researchers discovered that NAIP5 performs an in-depth inspection of bits of the bacteria's flagella, the tail-like appendages that many disease-causing bacteria use for locomotion. "This is a very effective immune response," says Vance, a microbiologist and immunologist, also at UC Berkeley. "It helps us understand why the pathogen can't escape just by mutating."

"Bacteria can't simply hide from the immune system by making minor changes to flagella proteins, he explains. And larger changes that might let bacteria evade detection could meddle with locomotion.

"The team tested the idea by creating mutant strains of Legionella and introducing them to the immune system proteins. Sure enough, minor mutations to a bacterial flagella protein weren't enough to trick NAIP5. But more significant mutations interfered with the flagella so much that the bacterium had trouble moving around.

"Intensive frisking by the immune system suggests that it is careful to identify a threat before taking out the big guns, Vance says. After glomming onto the bacterial protein snippet, the immune system protein recruits a second protein, forming a complex called an inflammasome. The second protein then sounds an alarm that the cell has been invaded, triggering events that culminate in a dramatic form of cell death.

"'The cell literally bursts open," Vance says. This dramatic finale—called pyroptosis—is a good thing if a bacterium is trying to take up residence in a cell, he says, but the chain of events can provoke disease if it happens too often. That's why it's important that the immune system is thorough, and the response is highly specific to the bacterium's flagella, he says. "

Comment: The immune system cells learn about bacteria by experience, changing its DNA to fit its discoveries. A newborn baby relies on its Mother's IGG, etc. antibodies in colostrum to start off life protected until it can build its own protection. This complexity has to be designed. Not by chance. How much complexity has to be shown in living evolved organisms before agnostics recognize design is necessary?