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Scientists have rescued a mouse immune system that was overwhelmed by a systemic blood infection. But will this work in humans?
Scientists have discovered how infections that invade the whole body, like malaria, disable the immune system and prevent it from detecting and fighting other microorganisms.
The Australian and German researchers say the discovery may help scientists to develop vaccines that restore immunity in people with systemic or 'whole body' infections. 
They publish their research today online in the journal Nature Immunology.
The immune response is alerted when specialised sentries of the immune system, dendritic cells, detect a virus or bacteria.
They alert the immune system by capturing infected cells and displaying fragments or antigens of the pathogen on their surface in a process called cross-presentation.  
Lead researcher Dr Jose Villadangos, an immunologist from the Walter and Eliza Institute of Medical Research in Melbourne, says systemic infections such as malaria or sepsis, a bacterial infection of the blood, overstimulate dendritic cells.
This results in the immune system's critical alarm system shutting down.
"This doesn't occur in local infections because only a few dendritic cells are involved," Villadangos says.
"But in the case of malaria infections and sepsis, dendritic cells throughout the body are concentrated on alerting the immune system, which prevents them from detecting and responding to any new infections." 
A new type of vaccine?
Villadangos and colleagues managed to restore immunity in mice with an immune system compromised by sepsis.
They injected them with a live vaccine made of dendritic cells that had been exposed to a secondary virus in the laboratory, and subsequently displayed antigens of that virus. 
Villadangos says the findings show the missing link in the immunosupressed animal is the capacity of the dendritic cells to display the antigens of new viruses. 
"We should be able to take dendritic cells from a patient with sepsis or malaria and expose them to antigens of the virus of a secondary infection and inject them back into the patient.
"This strategy is already being used in the development of anti-cancer vaccines. We are yet to find out if will work against secondary infections in humans with a systemic infection," Villadangos says.

Scientists will analyse the contents of this capsule for clues about how the solar system began
A seven-year quest to return to Earth pristine samples from the solar system's formation ended in triumph in a dark and wet Utah desert at the weekend. 
"It's hard to describe what it feels like to be at this point of the mission," University of Washington researcher and lead scientist of the Stardust mission Professor Don Brownlee said shortly after the probe's touchdown at 10:10 UTC (21:10 AEDT) on Sunday. 
"We travelled almost 3 billion miles in space. We visited a comet, grabbed a piece of it and it landed here this morning," Brownlee said. "It's an incredible thrill." 
Stardust released its precious cargo during a high-speed flyby of Earth, sending the tyre-sized canister soaring through space at a blazing speed of about 46,000 kilometres per hour when it smashed into the planet's atmosphere.
This makes it the fastest human-made object, topping the record set in May 1969 by the returning Apollo 10 command module. 
As its heat-shield fried away, a comet-like plume formed in its wake, looking like a torch that was visible in parts of the western US. 
"We weren't quite sure how bright it was going to be and some people didn't think we would see anything," says Brownlee, who slipped outside the Utah base with some of his team members to try to spot the capsule's streak across the sky. 
After scanning the sky for several minutes, Brownlee finally found an object that he said looked like Mars, but was clearly not where Mars was at the time. 
"It was twinkling a little bit, getting a little brighter, and moving. I thought, maybe that's a helicopter. But it kept getting brighter and brighter and brighter," he says. 
The object was reddish in colour and trailed a bright, glowing plume behind it, Brownlee says.
"It's ironic, you have a comet mission that ends producing a comet." 
Collecting spacedust
During its time in space, Stardust passed by Comet Wild-2 (Vilt-2) and extended a gel-filled collecting device to trap some particles to take back to Earth. It also collected bits of interstellar dust. 
Scientists believe comets contain unaltered material that was used to form the solar system. 
"We did this mission to collect the most primitive materials we could in the solar system," Brownlee says.
"We went to a comet that formed at the edge of the solar system, far from the Sun under very cold conditions. We're confident that it was made out of the initial building blocks of our solar system." 
The capsule was retrieved by helicopter crews and taken to a clean room on the Utah Test and Training Range for inspection.
The canister containing the samples is scheduled to be removed from the capsule and flown to the NASA Space Center in Houston on Tuesday. 
There, scientists will catalogue the samples and begin distributing them to teams for analysis.

Gotcha! A colourful, striking image can spark your interest
Internet users can take just one-twentieth of a second to decide whether they like the look of a website, new research has found.
"Visual appeal can be assessed within 50 milliseconds, suggesting that web designers have about 50 milliseconds to make a good impression," the Canadian researchers report in the March/April issue of the journal Behaviour & Information Technology.
Dr Gitte Lindgaard and colleagues from Carleton University in Ottawa confirm that internet users are a fickle lot.
The team did this by flashing up websites for 50 milliseconds and asking participants to rate them for visual appeal.
When they repeated the exercise after a longer viewing period the ratings were consistent.
The medium is the message
The finding comes as bad news to anyone hoping to convey information, says Sue Burgess, an Australian researcher who evaluates website useability and senior lecturer in information management at the University of Technology Sydney.
"There's no doubt that people do respond very quickly to websites and decide very quickly whether to stay on them," she says.
The appeal of a website is usually tied to colour, movement and interactivity, she says, with the way the information is structured coming second.
Burgess says it's unclear whether the internet is changing our ability to concentrate for long periods our if we are adapting to the medium.
"There's so much information and ... there's always going to be a lot of clicking around just to see what's there," she says.
The halo effect
Australian associate professor of psychology Bill von Hippel, from the University of New South Wales, says it takes about 50 milliseconds to read one word, making this a "stunningly remarkable" timeframe in which to process the complex stimuli on a website.
"It's quite remarkable that people do it that fast and that it holds up in their later judgement," he says.
"This may be because we have an affective or emotional system that [works] independently of our cognitive system."
In evolutionary terms, this ability helped us respond rapidly to dangerous situations, he says.
The study also reflects the so-called halo effect, von Hippel says, where an initial bias towards something drives subsequent judgements.
"This suggests that we make very quick judgements based on some sort of emotional reaction and our more considered judgements still reflect that first impression."

Jewish people's history and migrations are reflected in their DNA, a new study shows
Four Jewish mothers who lived 1000 years ago in Europe are the ancestors of 40% of all Ashkenazi Jews alive today, international researchers report.
The DNA study paints a vivid picture of human evolution and survival, and correlates with the well-established written and oral histories of Jewish migrations, says Dr Doron Behar of the Technion-Israel Institute of Technology, who worked on the study. 
The study, published in the American Journal of Human Genetics, suggests that some 3.5 million Jews alive today descended from four women. 
For their study, Behar and scientists from Europe and the US sampled DNA from 11,452 people from 67 populations.
"All subjects reported the birthplace of their mothers, grandmothers, and, in most cases, great-grandmothers," the scientists write. 
They looked at mitochondrial DNA, which is found in cells, outside the nucleus and away from the DNA that carries most genetic instructions.
Mitochondrial DNA is passed down virtually unchanged from mother to daughter, but it does occasionally mutate, at a known rate. 
Researchers can use this molecular clock to track genetic changes through time.
They used it, for instance, to compute when the "ancestral Eve" of all living humans lived: in Africa, about 180,000 years ago. 
Now they have found four ancestral Jewish mothers. 
"I think there was some kind of genetic pool that was in the Near East," Behar says.
"Among this genetic pool there were four maternal lineages, four real women, that carried the exact specific mitochondrial DNA markers that we can find in mitochondrial DNA today." 
Settling Europe
They, or their direct descendants, moved into Europe. 
"Then at a certain period, most probably in the 13th century, simply by demographic matters, they started to expand dramatically," Behar says. 
"Maybe it was because of Jewish tradition, the structure of the family that might have been characterised by a high number of children."
But these four families gave rise to much of the population of European Jews, which exploded from 30,000 people in the 13th century to "something like 9 million just prior to World War II", Behar says.
The Nazis and their allies killed 6 million Jews during the war, but there are now an estimated 8 million Ashkenazi Jews, defined by their common northern and central European ancestry, cultural traditions and Yiddish language. 
Behar says as they sampled people from Ashkenazi communities around the world, the same mitochondrial genetic markers kept popping up.
They did not find the markers in most of the non-Jewish people they sampled, and only a very few were shared with Jews of other origin.
Ancestry not genetic disease
This particular study does not provide a direct explanation for some of the inherited diseases that disproportionately affect Jews of European descent, such as breast and colon cancer, because most diseases are caused by mutations in nuclear DNA, not the DNA studied by Behar's group. 
These genes are believed to date from a 'bottleneck' phenomenon, when populations were squeezed down from large to small and then expanded again.
Behar and Skorecki's team have found what is known as a 'founder effect', when one or a small number of people have a huge number of descendants.

Scientists hope to gain an insight into the secret life of clouds with Australia's biggest climate experiment
International storm chasers gathering in Australia this week will release more than 1000 weather balloons over the next month as part of the nation's largest meteorological study.
The Tropical Warm Pool International Cloud Experiment, based in Darwin, will provide the world's most comprehensive set of data about the behaviour of thunderclouds, says Dr Peter May, a principal research scientist at the Australian Bureau of Meteorology in Melbourne.
May says the study will give scientists better ways of modelling cloud behaviour, resulting in more accurate short-term weather forecasting and better predictions for long-term climate change.
"The biggest uncertainty in climate forecasts and greenhouse calculations comes down to our understanding of thunderstorms," he says.
"The underlying aim of this experiment is to increase our understanding of thunderstorms themselves, how they evolve and the large scale impact they have."
Collaborators in the project include the bureau, the US Department of Energy Atmospheric Radiation Measurement Program, the CSIRO, NASA and universities from Australia, the US, Europe, Canada and Japan.
Measuring ice crystals
May says the tropical weather conditions in Darwin, which was devastated by Cyclone Tracy in 1974, provide a natural laboratory for storm watchers.
And this is the time of year for tropical storms, when Darwin has its monsoon-like 'wet' season.
The multi-million dollar study will have three prongs. 
May says research planes will fly directly into the clouds to measure ice crystals while a ground-based network will use radars, laser and infrared systems to look at cloud characteristics and the movement of heat, moisture and light.
And weather balloons will be released every three hours over 23 days from five sites around Darwin.
"This data set is going to be a real resource for the whole meteorological community," May says.
"It'll be the data set that people go to develop new model systems for the next 20 years. There will be dozens, if not hundreds of papers written about this experiment."
May says the link between climate change and global storm patterns is unclear.
But he says it's unlikely that climate change is directly responsible for isolated events, like Hurricane Katrina that struck New Orleans last year.
"The question isn't is a particular storm due to climate change, the question is are we loading the dice so that we can expect more storms or will they be more intense," he says.