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 encountered before.
The structure is strategically positioned on the outside of lymph glands 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.
These SPFs only appear when the mice immune systems are fighting off infections that have been encountered before.
What’s more, the researchers detected SPFs in human lymph nodes too, suggesting our bodies react in the same way.
“When you’re fighting bacteria that can double in number every 20 to 30 minutes, every moment matters,” says senior researcher Tri Phan. “To put it bluntly, if your immune system takes too long to assemble the tools to fight the infection, you die.”
“This is why vaccines are so important. Vaccination trains the immune system, so that it can make antibodies very rapidly when an infection reappears. Until now we didn’t know how and where this happened.”
Traditional microscopy approaches analyse thin 2D slices of tissue, and the researchers think that’s why SPFs haven’t been spotted before – they themselves are very thin, and they only appear temporarily.
In this case the team made the equivalent of a 3D movie of the immune system in action, which revealed the collection of many different types of immune cell in these SPFs. The researchers describe them as a ‘one-stop shop’ for fighting off remembered infections, and fighting them quickly.
Crucially, the collection of immune cells spotted by the researchers included Memory B type cells – cells which tell the immune system how to fight off a particular infection. Memory B cells then turn into plasma cells to produce antibodies and do the actual work of tackling the threat.
“It was exciting to see the memory B cells being activated and clustering in this new structure that had never been seen before,” says one of the team, Imogen Moran.
“We could see them moving around, interacting with all these other immune cells and turning into plasma cells before our eyes.”
According to the researchers, the positioning of the SPF structures on top of lymph nodes makes them perfectly positioned for fighting off infections – and fast.
They’re strategically placed at points where bacteria would invade, and contain all the ingredients required to keep the infection at bay.
Now we know how the body does it, we might be able to improve vaccine techniques – vaccines currently focus on making memory B cells, but this study suggests the process could be made more efficient by also looking at how they transform into plasma cells through the inner workings of an SPF.
“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,” says Phan.
“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 research has been published in Nature Communications.
Source: Science Alert