Scientists Discover New ‘Micro-organ’

Scientists have discovered a new “micro-organ” within the immune system, according to a study published in the journal Nature Communications.

Researchers from Australia’s Garvan Institute of Medical Research identified a structure that “remembers” past infections and vaccinations—and is filled with immune cells of many kinds which respond to pathogens that the body has seen before.

The structure is strategically positioned to detect infections early, according to researchers. It was discovered when the team used an advanced imaging technique, known as 3D microscopy, to essentially create “movies” of the immune system in action inside living animals.

Humans have long known that people who are exposed to an infection are often left with some immunity afterwards. However, certain questions still remain regarding exactly how this process works.

The structure, which extends over lymph nodes, is thin, flat and only appears when animals are exposed to an infection that the body has seen before. Named SPFs—or “subcapsular proliferative foci”—researchers detected the structures in both mice and humans.

When the team used microscopy techniques to view SPFs in the body, they saw several different types of immune cells, including “memory B Cells” which carry information about how best to attack infections.

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Crucially, the scientists observed that the memory B cells were changing into plasma cells—which make antibodies that can fend off pathogens.

“It was exciting to see the memory B cells being activated and clustering in this new structure that had never been seen before,” Imogen Moran, first author of the study from Garvan, said in a statement. “We could see them moving around, interacting with all these other immune cells and turning into plasma cells before our eyes.”

The location of the SPF structures is also perfectly suited to fighting infection, according to Tri Phan, who led the research.

“Now, we’ve shown that memory B cells rapidly turn into large numbers of plasma cells in the SPF,” Phan said. “The SPF is located strategically where bacteria would re-enter the body and it has all the ingredients assembled in one place to make antibodies—so it’s remarkably well engineered to fight reinfection fast.”

The researchers say that the structures had never been identified before because traditional microscopy techniques only look at thin 2D sections of tissue. This makes it hard to detect SPFs which are thin and not present at all times.

“So, this is a structure that’s been there all along, but no one’s actually seen it yet, because they haven’t had the right tools,” Phan said. “It’s a remarkable reminder that there are still mysteries hidden within the body—even though we scientists have been looking at the body’s tissues through the microscope for over 300 years.”

The latest results could help scientists to better understand how to develop more effective vaccines, according to the researchers.

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