One kind of immune cell exists purely to stop your own immune system from attacking you
Shimon Sakaguchi identified regulatory T cells in 1995, overturning the assumption that immune tolerance is set only early in life. Mary Brunkow and Fred Ramsdell later traced a mutated gene, FOXP3, behind a severe autoimmune disease in mice and humans. Together their work explained how the body keeps its own defenses from turning on itself, earning the 2025 Nobel Prize in Physiology or Medicine.