This study reveals how the human immune system recognizes chitosan, a natural component found in the walls of disease-causing fungi like Aspergillus and Cryptococcus. Researchers discovered that immune cells use a protein called CR3 on their surface to detect and respond to chitosan by producing inflammatory chemicals that help fight infection. When chitosan works together with fungal proteins, it can boost the immune system’s response even more effectively, suggesting new ways to enhance immunity against fungal infections.