Your immune system has a vote, even if you probably don't know it. As you read this, 1,8 trillion cells are patrolling your body, searching for viruses, bacteria, and tumor cells. Some are functioning well. Others aren't. Together, they form your immune system. immunome: a universe of molecular interactions that determines whether you get sick or stay healthy. Until now, medicine could only take blurry pictures of this system. Count a few types of cells. Measure generic proteins. There is now a test that scans it completely. Is called HMI and analyzes a million immune components from a sample. It returns a score, and this score tells you whether your immunome is working or hiding something. Even before symptoms appear. Do I have your attention? Good. Let's continue.
When a message changes your perception of health
The story begins with a text. "David, you are the red dot," he writes. John TsangYale immunologist (pictured). The attached image shows a graph with dozens of black dots scattered across a Cartesian plane. And a single red one, isolated. Below is a number: 0,35. No immediate explanation. The recipient of the message is David Ewing Duncan, a journalist who has been undergoing every new medical test available for twenty years. He had his DNA sequenced in 2001, when it cost a fortune. Not only that: he mapped proteins, microbiome, and metabolome. He amassed terabytes of data on himself. But this test promised something different. Not a list of numbers: a complete assessment of the health of his immunome.
The graph showed healthy people on the right, sick people on the left. The red dot was in the middle, slightly to the right. Duncan was 67 years old. He'd had COVID twice. Long COVID. Stress, infections, the passing of time. Yet his... immunome score It matched that of people 20 years younger. Not bad, considering everything. But what did that number really mean? And most importantly: what did it reveal that other tests had never revealed?
The immunome is a system that medicine still cannot read.
The immune system is made up of 1,8 trillion cells. Trillions of proteins, messenger RNA molecules, and metabolites. Each element changes continuously based on what you encounter: viruses, bacteria, food, stress, trauma.immunome It's this: the sum of all the interactions between immune components at a given moment. It's shaped by DNA, but also by everything you've experienced: past illnesses, the air you've breathed, the food you've eaten, the accumulated moments of tension. It's a living archive of your biological existence.
And until recently, medicine could only observe it from afar. Standard blood tests measure just a few markers: white blood cells, neutrophils, lymphocytes, and monocytes. It's like checking if a city is functioning by counting how many cars are on the street.It doesn't tell you if traffic is flowing, if the traffic lights are working, or if someone is blocking an intersection. The CBC (complete blood count) test, used for decades, counts cells. It doesn't assess what they're doing, it doesn't measure how they interact. Above all, it doesn't predict whether the system is about to fail or is already fighting something hidden.
The test developed by Tsang and his team at Yale goes further. It analyzes up to one million cells, proteins, RNA and immune biomoleculesIt doesn't just count them: it evaluates how they react, how they activate, how they communicate with each other when they encounter a threat. It uses machine learning algorithms to compare this data with that of thousands of other people and builds a complete profile of the immunome. The result is a number:Immune Health Metric, or IHM. A score that places each person on a scale between “immunoma healthy” and “immunoma compromised.”
The test that finds invisible diseases
In 2024, Tsang and Rachel Sparks, clinical immunologist now in AstraZeneca, they published the results of their study su Nature MedicineThey tested 270 people: 228 with rare genetic diseases that compromise the immune system and 42 healthy individuals. The test analyzed their blood for distinctive signs of compromised immunosuppression. And it found them. People with different diseases showed similar patterns: low levels of natural killer cells, alterations in cytokines, imbalances in specific proteins. The test was able to distinguish those who were ill from those who were not.
But then came the interesting discovery. Some "healthy" people appeared on the graph next to the sick. Other sick people were on the side of the healthy. About half of people are undiagnosed Their IHM scores overlapped with those with full-blown illnesses. Possible explanations: either they were fighting a passing virus (like an incubating cold), or their immune system was compromised by age and accumulated stress, or they were harboring something that hadn't yet shown symptoms. A latent autoimmune disease. A microscopic tumor. A chronic, yet-silent inflammation.
“The CBC doesn't tell me what the cells I'm counting are doing,” Sparks explains. “I just know there are more neutrophils than normal. But they could be behaving poorly or well. We now have technologies that allow us to see at a granular level what a cell actually does when a virus appears.. How it changes, how it reacts, whether it activates or remains still.”
Why some people get sick and others don't
The pandemic exposed a problem. Young, seemingly healthy people were dying of COVID. Other elderly women with underlying health conditions were getting along with mild fevers. No one could explain why. Stephen Hawking He had been warning for years that revealing our presence in the universe could be risky (it has nothing to do with it, but the principle is similar: you never know what's out there). It's the same with viruses: you never know how you'll react until you encounter them. And when you do, it's often too late to prepare.
“One of the most surprising aspects of the pandemic has been seeing apparently very healthy young people become seriously ill and then die,” says Mark Davis, Stanford immunologist who helped found the field of systems immunology. “Some had obesity or diabetes. Others didn't. The question is: Could we have known in advance that something was wrong with their immune systems? Could we have diagnosed it and warned them to take extra precautions?”
The immunome test is designed to answer this question. By measuring the baseline state of the immune system, it can predict who will respond better or worse to an infection. Or to a vaccine. There are already tests today. detailed protocols to manage unexpected scenarios (ok, that one was talking about aliens, but the principle also applies to pandemics). The difference is that with IHM, you can know in advance if you're at risk. Not because of age or pathologies, but because of the actual state of your immunodeficiency virus.
How the immunome score works
The test starts with a blood draw. It's nothing invasive. From there, the sample is subjected to a battery of analyses: RNA sequencing to see which genes are active in immune cells, measurement of hundreds of circulating proteins, and high-resolution counting of dozens of different cell types. The data is processed by algorithms that compare it with a database of thousands of healthy and sick people. Artificial intelligence searches for patterns, correlations, and weak signals that indicate a compromised state of health.
The result is a number on an arbitrary scale. Like when in high school they gave you a grade from 1 to 10 and you didn't really understand what the 7 meant.Except that here the score is built on solid statistical foundations. The higher it is, the better the immunome functions. The lower it is, the more stressed or compromised the system is. Tsang's team validated the score in several independent studies. They demonstrated that the IHM predicts response to vaccines: those with high scores develop more antibodies. They then showed that it reflects the activity of autoimmune diseases like lupus: as symptoms worsen, the score drops. They also correlated with body mass index, even controlling for age, sex, and ethnicity.
The test also revealed something interesting about aging. The biological age of the immunoma does not correspond to the chronological ageSome 70-year-olds have immunomassed like 40-year-olds. Others in their 40s appear to be 70-year-olds from an immune standpoint. David Duncan, the journalist at the Red Dot, discovered that his immunoma was about 47 years old. He was 67. A result that surprised him, considering (as mentioned) two episodes of long COVID and decades of work-related stress.
The project to map the global immunome
Tsang and his colleague Shai Shen-Orr, from the technion Israelis have an ambitious plan. They want to test hundreds of thousands of people around the world. Not just Americans and Europeans, but Africans, Asians, South Americans, and Australians. Because the immunodeficiency varies depending on the environment. An example? A vaccine developed in Maryland could work very well there but fail in Tanzania. Not because the vaccine is defective, but because the immunological systems of the two populations are different. Different genetics, different diets, different pathogens, different climates. All contribute to shaping the immune system.
In 2022, Tsang and Shen-Orr met Jane Metcalfe, co-founder of Wired, who had just become president of the Human Immune System Project (HIP). The organization was founded in 2016 to develop better vaccines, but had recently changed its mission: to decode the human immunome on a global scale. "We have advanced molecular profiles developed in Palo Alto and Tel Aviv," said Metcalfe, "but we can't understand the variability of the immune system if we only test small groups in a few cities. We need sites everywhere to build real predictive models."
The plan is to start with a pilot study in Africa, Australia, East Asia, Europe, the United States, and Israel. Test a few thousand people. Then expand to 150 sites worldwide and evaluate approximately 250.000 individuals. The ultimate goal: create a public database of the human immunome accessible to every researcher. A global infrastructure to understand how the immune system responds to infections, vaccines, drugs, and environmental stressors. And to develop personalized therapies based on each patient's actual immunoma status.
The estimated cost is about $3 billion over 10 years. HIP plans to raise funds by combining public and private funds, collaborating with governments and international agencies. Cuts in federal funding for biomedical research in the United States could complicate matters, but the organization aims to diversify its sources. The project is already supported by institutions such as the Gates Foundation and involves universities and research centers around the world.
What happens when the immunoma ages
Aging affects the immune system in predictable ways. T cells become less reactive. The production of new lymphocytes slows. The bone marrow, which generates immune cells, becomes less efficient. Chronic low-grade inflammation (called inflammation) accumulates. The result: greater vulnerability to infections, tumors, and autoimmune diseases. But the process isn't the same for everyone. Some people maintain robust immune systems into their 80s. Others show signs of decline as early as 50.
Shen-Orr developed a variant of the test called IMM-AGE, which calculates the biological age of the immunome based on cellular composition and protein levels. Her team used this data primarily to assess cardiovascular risk: a prematurely aged immunome correlates with a higher risk of heart attack and stroke. When Duncan took the IMM-AGE test, he had an immune age of 57, compared to his chronological age of 67. A good result, but not exceptional. Shen-Orr envisions a future where people check their immunome score on an app after every blood test, similar to how you check your heart rate or blood pressure today.
The idea is simple: if you can measure something, you can try to improve itAn immunoma with a low score could benefit from targeted interventions: stress reduction, improved sleep, a more balanced diet, and exercise. Or, in more severe cases, immunomodulatory therapies. Treatments already exist that boost regulatory T cells to control autoimmune diseases, or suppress them to allow the immune system to better attack tumors. But these are experimental approaches, still far from routine clinical use.
The guardian cells that won the Nobel Prize
October 2025. The Nobel Prize in Medicine he just went to Mary Brunkow, Fred Ramsdell e Shimon Sakaguchi for the discovery of regulatory T cells. They are the "security guards" of the immunoma: they prevent the immune system from attacking healthy tissue. Without them, the body self-destructs. With too many, tumors grow unchecked because the immune system remains blocked. The gene FOXP3, identified by Brunkow and Ramsdell in 2001, controls the development of these cells. Mutations in that gene cause devastating autoimmune diseases such as IPEX syndrome.
The discovery has opened a new therapeutic frontier. Boosting regulatory T cells could cure type 1 diabetes, multiple sclerosis, and lupus. Reducing them could help cancer immunotherapy work better. Immunoassays can measure the levels of these cells and predict whether a patient will respond to therapies that modulate them. It's a concrete example of how understanding the immune system at the molecular level changes the approach to medicine.
“Their discoveries have been crucial in understanding why we don't all develop serious autoimmune diseases,” he said. Olle Kampe, president of the Nobel Committee. Sakaguchi, 74, told Japanese journalists: "It's an honor, but above all a victory for those who believe that the human body can also stop, not just attack."
When will we all be able to get the immunome test?
For now, the immunoma test remains experimental. You can't ask your GP for it. It's too expensive, requires sophisticated technology, and requires specialized personnel. But Rachel Sparks is optimistic:
"I think in 10 years we'll have something usable in the clinic. I'll be able to use this granular understanding of what the immune system does at the cellular level in my patients. And I hope we can target therapies directly to the cells or pathways that contribute to disease."
Mark Davis agrees: "With a little effort, we could actually have something useful in 10 years." The process is slow. Validated standards, shared protocols, and large-scale studies are needed to demonstrate that the test actually works. And healthcare systems need to be convinced to pay for a test that costs significantly more than a traditional CBC. But the potential is there. Identify diseases before the symptoms can save lives. Predicting vaccine responses can optimize immunization campaigns. Understanding why some people age better than others can help everyone age better.
Metcalfe envisions even broader applications.
"We could link immunome data with rising global temperatures to study how climate change affects the immune system of a newborn or pregnant woman. This data could be integrated into models that help us understand the effects of pollution, nutrition, and climate on human health."
The Red Dot and the Future of Medicine
David Duncan got his score. 0,35 on an arbitrary scale. A healthy immunoma, placed among people 20 years younger. A result that doesn't reveal granular details (like why he had long COVID twice while others didn't), but it offers a general assessment of the state of the system. "Your score always changes based on your exposure and your age," Tsang told him. "The IHM is still so new that it's hard to know exactly what it means until we do more work. And until HIP can evaluate thousands or hundreds of thousands of people."
We'll also need to continue testing Duncan over time to see how his immunome evolves. How it changes after an infection, after a period of stress, after years. Numbers alone aren't enough. Context and history are needed. We need to understand where he's going, not just where he is now. But in the meantime, for the first time, there's a way to measure something that was previously invisible. It's like discovering that you can weigh thoughtsIt's not perfect, but it's a start.
Duncan concludes his experience on a note of caution and curiosity: “I wonder what the immune circuitry inside me might still reveal about whether I’m truly healthy right now, or whether I’ll be healthy tomorrow, next month, or years from now.” The question remains open. The immunome continues to change. And the test continues to evolve. Perhaps in 10 years, we’ll be checking the score like we check our blood sugar today. Perhaps it will become routine. Or perhaps we’ll discover that knowing too much creates more anxiety than benefits.
Meanwhile, the red dot on the graph remains there. A number that says something, but not everything. Not enough to reassure us, but better than nothing.
Tomorrow, that number could tell us everything.
