The immune system ages differently in women and men. Women may pay a higher price for stronger immune responses

A new single-cell analysis shows that immune aging does not follow the same pattern in women and men. These differences may help explain distinct risks of infection, autoimmunity, and some blood cancers.

The immune system ages differently in women and men. Women may pay a higher price for stronger immune responses

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    Immune aging does not follow one universal script

    The immune system does not age through a simple loss of function. With age, the composition of immune cells, their activity, and the way they regulate inflammation all change. This process is known as immunosenescence, and it can influence susceptibility to infections, cancer, autoimmune diseases, and vascular disease.

    A new study published in Nature Aging shows that this process does not look the same in women and men. The authors analyzed more than one million immune cells and found that women showed stronger age-related changes, especially in areas linked to immune activation and the expression of genes associated with autoimmunity.

    The key message is not that women have a “better” or “worse” immune system. A more accurate interpretation is that women and men may age immunologically according to different patterns, and those patterns may shift disease risk in different directions.

    Study details

    • Publication title: Single-cell analysis of the human immune system reveals sex-specific dynamics of immunosenescence.
    • Authors: Maria Sopena-Rios, Aida Ripoll-Cladellas, Fatemeh Omidi, Sara Ballouz, Jonathan Alquicira-Hernandez, Ruben Oelen, Alex W. Hewitt, Lude Franke, Monique G. P. van der Wijst, Joseph E. Powell, Marta Melé.
    • Publication year: 2026.
    • Journal: Nature Aging.
    • DOI: 10.1038/s43587-026-01099-x.
    • Publication link: Nature Aging.
    • Study type and design: single-cell analysis of the immune system, assessing age- and sex-dependent changes.
    • Population and sample: 416 men and 566 women aged 19 to 97 years.
    • Biological material: peripheral blood mononuclear cells, or PBMCs.
    • Scale of analysis: more than 1 million immune cells analyzed.
    • Main analytical axes: participant age, biological sex, immune cell subtype, and gene expression.
    • Main finding: the study identified both shared and sex-specific patterns of immune aging, including stronger age-related gene expression changes in women.

    This study matters not because it offers a ready-made intervention, but because it shows how much averaging biological data can hide clinically relevant differences.

    What exactly differed between women and men?

    A key strength of this study was its cell-by-cell approach, rather than relying only on bulk measurements of average immune system activity. This allowed the researchers to see which specific immune cell populations changed with age in women and which changed in men.

    In women, the study found more pronounced changes in cell populations linked to cytotoxic responses, antiviral defense, and inflammation. In men, one especially important finding was the accumulation of certain B cells, which may be relevant to hematological disease risk.

    The most important differences included several areas:

    • In women, CD8+ T_EM cells, or effector memory T cells, were more enriched with age. These cells may participate in the elimination of virus-infected cells and tumor cells.

    • In women, CD14+ monocytes also increased with age. These cells are involved in inflammatory responses, which may support antiviral defense but may also contribute to the chronic, low-grade inflammation typical of aging.

    • In men, naive B cells, including the CD5+ B-cell subtype, were enriched with age. The authors point out that these changes may be relevant to the higher prevalence of some lymphocytic diseases in older men.

    • In gene expression, only part of the age-related changes were shared between sexes. Women showed more unique aging-related changes, suggesting stronger immune remodeling with age.

    One especially interesting finding was that the largest gene expression shifts appeared later in life — around age 70 in women and slightly later in men. This suggests that sex differences in immune aging may become more pronounced in the second half of life.

    Stronger immunity may come with a cost

    Women often show stronger immune responses than men. On one hand, this may mean better protection against some infections. On the other hand, the same feature may increase the risk of the immune system reacting too strongly or in the wrong direction.

    This paradox is one of the most important themes of the study. Greater immune activity can be useful when facing a pathogen, but it may also increase susceptibility to autoimmune diseases, in which the body attacks its own tissues.

    The study identified several observations that support this interpretation:

    • In women, age-related changes were stronger in the expression of genes linked to autoimmune functions. This does not automatically mean disease, but it points to a biological background that may increase susceptibility.

    • Autoimmunity-related genes increased their activity with age in both women and men, but in women older than 50, their levels were higher than in men.

    • Changes in women’s immune cell populations involved cells active in cytotoxicity, inflammation, and antiviral defense. This profile may be beneficial in one context and problematic in another.

    • The findings fit earlier epidemiological observations showing that many autoimmune diseases are more common in women than in men.

    The point is not that the female immune system is simply “better” or “worse.” A more precise conclusion is that it may be more reactive, and with age, this reactivity may carry greater consequences.

    Differences in disease risk may begin at the cellular level

    Immunosenescence has practical relevance because the immune system influences many systems at once. It is not only about infections. Chronic inflammation, impaired tumor surveillance, and abnormal autoimmune activation can affect the entire body.

    The study helps explain why women and men may develop different health risk profiles with age.

    The most important potential implications are:

    • In women, stronger shifts toward immune activation may partly explain greater susceptibility to autoimmune diseases, such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, or multiple sclerosis.

    • In men, the increase in specific B-cell populations may be one biological clue helping explain the higher prevalence of some blood cancers, including chronic lymphocytic leukemia.

    • In both sexes, immune aging may contribute to inflammaging, the chronic, low-grade inflammatory state associated with many age-related diseases.

    • Differences between women and men may matter for future biomarkers of immune aging, because one “universal” marker may not describe risk equally well in everyone.

    This study does not yet show exactly how diagnostics or treatment should change. However, it does show that precision medicine for aging will need to take into account not only chronological age, but also biological sex, cell type, and gene expression patterns.

    Why this matters for longevity

    In the context of longevity, the immune system is one of the key systems regulating how health declines with age. It is responsible not only for fighting infections, but also for controlling inflammation, surveilling cancerous cells, repairing tissue, and communicating with other organs.

    The study shows that immune aging is more complex than simple claims about “boosting the immune system” suggest. In many cases, the goal is not maximum immune activation, but better regulation: a response strong enough to handle threats, but not so excessive that it promotes chronic inflammation or autoimmunity.

    From a practical perspective, three points stand out:

    • A stronger immune response is not always clearly beneficial. Over the long term, excessive immune activity may increase biological costs, especially if it promotes chronic inflammation.

    • Aging research should more often analyze data separately for women and men. Averaging results can hide mechanisms that are important for one group but weaker or different in another.

    • Biomarkers of immunosenescence may one day help assess age-related disease risk more precisely, but they need to be interpreted in the context of sex, age, health history, and specific cell type.

    The core message is simple: immunity also ages, but it does not do so according to one universal pattern. The better these differences are understood, the greater the chance of developing more precise prevention strategies for age-related disease.

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