Cell-autonomous immunity shaped human evolution

Date:
September 9, 2020
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Every human cell harbors its own defenses against microbial
invaders, relying on strategies that date back to some of the
earliest events in the history of life, researchers report. Because
this 'cell-autonomous immunity' is so ancient and persistent,
understanding it is essential to understanding human evolution
and human medicine, the researchers said.



FULL STORY ========================================================================== Every human cell harbors its own defenses against microbial invaders,
relying on strategies that date back to some of the earliest events in
the history of life, researchers report. Because this "cell-autonomous immunity" is so ancient and persistent, understanding it is essential
to understanding human evolution and human medicine, the researchers said.


==========================================================================
Like amoebae, most human cells can transform themselves to engulf and
degrade foreign agents in a process known as phagocytosis, said Jessica Brinkworth, a professor of anthropology at the University of Illinois, Urbana-Champaign who wrote the new report with former undergraduate
student Alexander Alvarado. And the methods that human cells use to
detect, pierce or hack up invading microbes are inherited from -- and
shared by -- bacteria and viruses, she said.

"Every cell has these things and they have this deep evolutionary
history," Brinkworth said. "This means that if you're going to study
humans, you need to accept that immunity is always going to be part
of what you're looking at. And you're going to have to go deep into evolutionary time." The authors reject the notion that the immune system
is distinct from other bodily systems.

"Immunity is literally everywhere," Brinkworth said. "The whole of the organism, from the skin down to the level of the last enzyme floating
anywhere in the body, almost all of it is engaged in protection in one
form or another." For that reason, she suggests that medical approaches
to fighting infection that try to tamp down evolutionarily conserved
immune responses such as pro- inflammatory pathways are misguided. While
it can be useful or necessary to use immune-suppressing drugs against autoimmune conditions or in the case of organ transplants, such drugs
do not appear to work against severe microbial infections.

"In the context of severe infections, there have been many attempts to
come up with ways of reducing the immune response by throwing a bunch of steroids at it or blocking the body's ability to detect the pathogen," Brinkworth said. "But targeting these immune mechanisms that have
been around for millions of years is potentially counterproductive."
In the case of sepsis, which Brinkworth studies, this approach has not
been fruitful.

"More than 100 trials of immunomodulatory approaches to sepsis have
failed," she said. "And the one drug that made it to market then
failed. Most of these drugs tried to block highly evolutionarily
conserved defenses, like mechanisms of cell-autonomous immunity."
Many immunomodulatory drugs now being tested against the new coronavirus
are failed sepsis drugs, she said.

Similarly, anthropologists often fail to consider how millions of years
of battle against infections at the cellular level have shaped human
genetics, physiology and even behavior, Brinkworth said.

"If you're talking about human evolution, if you're in any physiological system, you're going to have to address at some point how pathogens have
shaped it," she said.


========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Diana Yates. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Jessica F. Brinkworth, Alexander S. Alvarado. Cell-Autonomous
Immunity
and The Pathogen-Mediated Evolution of Humans: Or How Our
Prokaryotic and Single-Celled Origins Affect The Human Evolutionary
Story. The Quarterly Review of Biology, 2020; 95 (3): 215 DOI:
10.1086/710389 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200909114810.htm

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