Sydney — May 29, 2026 — A groundbreaking study has shed new light on why autoimmune diseases such as lupus and multiple sclerosis disproportionately affect women. Researchers in Australia analysed more than 1.25 million immune cells from 982 people, uncovering genetic differences that make female immune systems more prone to inflammation.
The findings, published in The American Journal of Human Genetics, revealed over 1,000 genetic “switches” that behave differently between the sexes. Women’s immune cells showed higher baseline activity in inflammatory pathways, offering stronger protection against viral infections and vaccines but also increasing the risk of the immune system mistakenly attacking healthy tissue.
The study found that women carried more B cells and naive CD4 T cells, which are central to antibody production and targeted immune responses — the same cell types often implicated in autoimmune conditions. Men, by contrast, had more “first responder” cells such as monocytes and natural killer cells.
Researchers also identified two sex‑specific genetic dials on the FCGR3A and ITGB2 genes, both linked to lupus. These differences suggest that autoimmune risk is not only influenced by sex chromosomes and hormones but is also embedded in the baseline genetic activity of immune cells.
While women’s heightened immune reactivity provides advantages in fighting infections, it comes with a trade‑off: a greater predisposition to autoimmune disease. The team argues that treatments should move beyond one‑size‑fits‑all approaches and be tailored to how a patient’s immune system operates at a genetic level.
As co‑author Joseph Powell of the Garvan Institute noted, “If we want to realise the potential of precision medicine, we have to understand these fundamental biological variables.”
This research underscores the importance of studying the immune system with sex differences in mind, paving the way for tailored autoimmune treatments and deeper insights into sex‑based immune responses.
