Nav: Home

Memory immune cells that screen intruders as they enter lymph nodes

March 31, 2015

Australian scientists have discovered a new population of 'memory' immune cells, throwing light on what the body does when it sees a microbe for the second time. This insight, and others like it, will enable the development of more targeted and effective vaccines.

Two of the key players in our immune systems are white blood cells known as 'T cells' and 'B cells'. B cells make antibodies, and T cells either help B cells make antibodies, or else kill invading microbes. B cells and killer T cells are known to leave behind 'memory' cells to patrol the body, after they have subdued an infection.

The newly identified 'Follicular Memory T cells' are related to the T helper cells but unlike circulating memory B and T cells, they position themselves near the entrance of lymph nodes, particularly those that are potential sites of microbe re-entry.

Humans have evolved an astonishing way of dealing with infection. When a microbe containing 'antigens' (parts of the microbe that trigger immune responses) penetrates the skin, it quickly gets transferred to our lymph nodes, which are interspersed throughout our bodies.

Lymph nodes are purpose-built structures for trapping microbes and manufacturing the antibodies needed to neutralise them. They contain clearly demarcated zones, populated by different kinds of immune cells, carrying out specialised tasks.

When a microbe arrives at the lymph node, it is trapped by sentinel immune cells, called subcapsular sinus macrophages, which have evolved to act as 'the flypaper of the lymph node'. This sets off a chain reaction that results in the formation of a 'germinal centre', from which antibody-producing cells are made.

Before this can happen, B cells have to be able to perceive the microbe and then pass a number of quality control filters to ensure only those cells best able to make neutralising antibodies are selected.

A subset of T helper cells, known as Follicular T helper (Tfh) cells, are critical for the antibody response because they help B cells navigate through these quality control filters. This process, from the arrival of a microbe to the creation of potent antibodies, is known as the 'primary antibody response' and is already well studied and described.

The new study examines the 'secondary antibody response', when the body next encounters the same invader. The findings are published in the prestigious journal Immunity, now online.

Dr Tri Phan, Dr Tatyana Chtanova, Dr Dan Suan, Dr Akira Nguyen and Imogen Moran, from Sydney's Garvan Institute of Medical Research, demonstrated that Tfh cells behave very differently during the primary and secondary responses.

During the primary response, they are confined within the germinal centre; during the secondary response they are free to leave the germinal centre and "surf the lymph system" in search of memory B cells to activate.

The researchers tracked the primary and secondary immune responses in mice, by using a laser to tag the cells deep inside the lymph node and then follow them with a special microscope that can be used in living animals.

"What we saw in the secondary response really surprised us," said Dr Tri Phan. "The memory cells weren't coming from the blood, as expected. They were already in the lymph node, and only in the lymph node closest to the original site of infection.

"This is important because, until now, people have thought that memory is provided by circulating cells.

"In addition to the memory cells that are on patrol in the circulation, we show that the immune system also leaves behind a garrison of memory cells - follicular memory T cells - strategically positioned at the entrance of the lymph node to screen for return of their particular microbe of interest.

"We could see the follicular memory T cells talking to subcapsular sinus macrophages - the highly specialised flypaper cells that trap antigen - checking their catch to see if it was of interest.

"When the memory cell sees its target on the macrophage, it becomes activated and the cell divides to start making a new army of Tfh cells. This second generation of Tfh cells is then sent out via the lymphatic system to other parts of the body to fight the infection.

"We think that the subcapsular sinus macrophages are incredibly important to the process. Understanding how to target antigen to them, and in turn to the memory cells, will help make better, more effective vaccines.

"The more insight we have into these complex processes from a whole body perspective, the better. Our laboratory is fortunate to have the technology that allows us to view cellular interactions as they play out in real-time on such a large scale."
-end-


Garvan Institute of Medical Research

Related Memory Articles:

Memory boost with just one look
HRL Laboratories, LLC, researchers have published results showing that targeted transcranial electrical stimulation during slow-wave sleep can improve metamemories of specific episodes by 20% after only one viewing of the episode, compared to controls.
VR is not suited to visual memory?!
Toyohashi university of technology researcher and a research team at Tokyo Denki University have found that virtual reality (VR) may interfere with visual memory.
The genetic signature of memory
Despite their importance in memory, the human cortex and subcortex display a distinct collection of 'gene signatures.' The work recently published in eNeuro increases our understanding of how the brain creates memories and identifies potential genes for further investigation.
How long does memory last? For shape memory alloys, the longer the better
Scientists captured live action details of the phase transitions of shape memory alloys, giving them a better idea how to improve their properties for applications.
A NEAT discovery about memory
UAB researchers say over expression of NEAT1, an noncoding RNA, appears to diminish the ability of older brains to form memories.
Molecular memory can be used to increase the memory capacity of hard disks
Researchers at the University of Jyväskylä have taken part in an international British-Finnish-Chinese collaboration where the first molecule capable of remembering the direction of a magnetic above liquid nitrogen temperatures has been prepared and characterized.
Memory transferred between snails
Memories can be transferred between organisms by extracting ribonucleic acid (RNA) from a trained animal and injecting it into an untrained animal, as demonstrated in a study of sea snails published in eNeuro.
An immunological memory in the brain
Inflammatory reactions can change the brain's immune cells in the long term -- meaning that these cells have an 'immunological memory.' This memory may influence the progression of neurological disorders that occur later in life, and is therefore a previously unknown factor that could influence the severity of these diseases.
Anxiety can help your memory
Anxiety can help people to remember things, a study from the University of Waterloo has found.
Pores with a memory
Whether for separation processes, photovoltaics, catalysis, or electronics, porous polymer membranes are needed in many fields.
More Memory News and Memory Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.