But then the results got really interesting. In a few cases, the immune systems of unhealthy and healthy people looked similar, with some people appearing near the “healthy” area of the chart even though they were known to have diseases. Most likely this was because their symptoms were in remission and not causing an immune reaction at the moment when their blood was drawn, Tsang told me.
In other cases, people without a known disease showed up on the chart closer to those who were known to be sick. “Some of these people who appear to be in good health are overlapping with pathology that traditional metrics can’t spot,” says Tsang, whose Nature Medicine paper reported that roughly half the healthy individuals in the study had IHM scores that overlapped with those of people known to be sick. Either these seemingly healthy people had normal immune systems that were busy fending off, say, a passing virus, or their immune systems had been impacted by aging and the vicissitudes of life. Potentially more worrisome, they were harboring an illness or stress that was not yet making them ill but might do so eventually.
These findings have obvious implications for medicine. Spotting a low immune score in a seemingly healthy person could make it possible to identify and start treating an illness before symptoms appear, diseases worsen, or tumors grow and metastasize. IHM-style evaluations could also provide clues as to why some people respond differently to viruses like the one that causes covid, and why vaccines—which are designed to activate a healthy immune system—might not work as well in people whose immune systems are compromised.
Spotting a low immune score in a seemingly healthy person could make it possible to identify and start treating an illness before symptoms appear, diseases worsen, or tumors grow and metastasize.
“One of the more surprising things about the last pandemic was that all sorts of random younger people who seemed very healthy got sick and then they were gone,” says Mark Davis, a Stanford immunologist who helped pioneer the science being developed in labs like Tsang’s. “Some had underlying conditions like obesity and diabetes, but some did not. So the question is, could we have pointed out that something was off with these folks’ immune systems? Could we have diagnosed that and warned people to take extra precautions?”
Tsang’s IHM test is designed to answer a simple question: What is the relative health of your immune system? But there are other assessments being developed to provide more detailed information on how the body is doing. Tsang’s own team is working on a panel of additional scores aimed at getting finer detail on specific immune conditions. These include a test that measures the health of a person’s bone marrow, which makes immune cells. “If you have a bone marrow stress or inflammatory condition in the bone marrow, you could have lower capacity to produce cells, which will be reflected by this score,” he says. Another detailed metric will measure protein levels to predict how a person will respond to a virus.
Tsang hopes that an IHM-style test will one day be part of a standard physical exam—a snapshot of a patient’s immune system that could inform care. For instance, has a period of intense stress compromised the immune system, making it less able to fend off this season’s flu? Will someone’s score predict a better or worse response to a vaccine or a cancer drug? How does a person’s immune system change with age?
Or, as I anxiously wondered while waiting to learn my own score, will the results reveal an underlying disorder or disease, silently ticking away until it shows itself?
Toward a human immunome project
The quest to create advanced tests like the IHM for the immune system began more than 15 years ago, when scientists like Mark Davis became frustrated with a field in which research—primarily in mice—was focused mostly on individual immune cells and proteins. In 2007 he launched the Stanford Human Immune Monitoring Center, one of the first efforts to conceptualize the human immunome as a holistic, body-wide network in human beings. Speaking by Zoom from his office in Palo Alto, California, Davis told me that the effort had spawned other projects, including a landmark twin study showing that a lot of immune variation is not genetic, which was then the prevailing theory, but is heavily influenced by environmental factors—a major shift in scientists’ understanding.
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