A landmark study by Yale and Fred Hutchinson Cancer Center found that naturally occurring autoantibodies can strongly affect patient responses to checkpoint immunotherapy. Certain autoantibodies were associated with up to a tenfold increase in tumor shrinkage likelihood, highlighting their role beyond autoimmune diseases. These insights propose autoantibodies as biomarkers or therapeutic targets to expand immunotherapy benefits. The findings, published in Nature, open pathways to personalized cancer treatment strategies leveraging humoral immune determinants.