Understanding Your Immune System: A Lifespan Journey

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Image credit: https://openai.com/index/dall-e/ 


Have you ever wondered how your immune system changes as you get older? It’s not just about catching colds, our immune system is always working hard to protect us and it’s constantly evolving throughout our lives. A new study has looked at how our immune system changes from birth right through to old age, providing some fascinating insights.


What the study did: Scientists looked at blood samples from a large group of healthy people, ranging from newborns to those over 90 years old. They used advanced techniques to study the different types of immune cells in these samples. They looked at how these cells behave and change over time. This is called a "single-cell atlas," because they looked at each cell individually.


Key findings

  • Immune cells change over time: The study identified 25 different types of immune cells in the blood. The number of each type of cell changes throughout life. Some become more common as we get older, while others become less common.
  • A new type of B cell: The researchers discovered a new type of B cell, which is a type of immune cell that makes antibodies. These are called B_BCR+GNLY+ cells and are particularly common in young children. These cells can kill other cells, and scientists think they might play a vital role in protecting children from infections. These cells are highest in the 6-year-old group, decrease at age 12 and are low in adults.
  • T cells and age: T cells are another crucial type of immune cell. The study found that the number of naive T cells, which are new T cells that haven’t encountered any infections before, decreases as we get older. Conversely, certain types of memory T cells, which have learned to fight specific infections, increase.
    • Early life clonal expansion: T cells that have expanded in response to an infection were shown to peak in childhood (ages 2–12). This indicates that children's immune systems are actively learning and adapting to their environment.
    • Late life clonal expansion: The study also found a second peak in these expanded T cells in the elderly (ages 70-90). This may indicate that older adults' immune systems are struggling to keep up with persistent infections or diseases.
  • MAIT cells in adolescence: A specific type of T cell called MAIT cells (CD8_MAIT_SLC4A10) was found to be particularly active during adolescence (ages 12–18). These cells help to fight off bacterial infections, and seem to be more capable of fighting off pathogens during this stage. The researchers even tested this in the lab and found that MAIT cells from young adults were more effective at killing bacteria than those from middle-aged adults. Interestingly, tuberculosis related signaling was reduced in MAIT cells during adolescence, aligning with the fact that this age group has the lowest rates of tuberculosis.
  • Cell communication changes: The study also looked at how immune cells communicate with each other. They found that these interactions change significantly as we age. T cells appear to experience the most changes in how they interact with other cells.
  • Immune checkpoints: The study looked at how immune checkpoints change across our lifespan. Immune checkpoints are molecules that regulate the immune response and help prevent overactivity of the immune system. The study showed that molecules like CD27, ICOS and PDCD1 are expressed differently across the lifespan.
  • Age-related genes: The researchers identified genes that show age-related changes in expression. The genes that are more active in older adults are involved in processes like inflammation, while the genes that are less active are linked to DNA and cell structure. Some genes like LGALS1 increase with age while CCR7 and TMIGD2 decrease with age.


What does this mean? This study helps us understand how the immune system changes over our lives. The data also shows how the immune system is different during childhood, adolescence, adulthood and old age. The study can help researchers better understand why older people are more vulnerable to infections and diseases. This research has led to the creation of an immune age prediction model, called siAge. This model uses machine learning to predict a person’s immune status. This could be used to assess if a person’s immune system is aging faster or slower than expected.


The future: This is a really exciting area of research, and scientists hope that it can lead to new ways of treating diseases and keeping people healthy as they age. The researchers have made their data and the siAge tool publicly available, meaning other scientists can use their work to make even more discoveries. This study highlights the importance of our immune systems and how we need to support them throughout our lives.

In short, the study provides a great resource for understanding the development of our immune systems across our whole lives. The data is available online for anyone interested in exploring these exciting findings further.

 

Additional information: Integrating single-cell RNA and T cell/B cell receptor sequencing with mass cytometry reveals dynamic trajectories of human peripheral immune cells from birth to old age. Nature Immunology (2025). https://doi.org/10.1038/s41590-024-02059-6

Journal information: https://www.nature.com/ni/


Location: Oxford, UK

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