Researchers isolated and studied a polysaccharide compound from oyster mushrooms (Pleurotus abieticola) called PAPS1. When tested in mice treated with a chemotherapy drug that suppresses immunity, PAPS1 helped restore immune function by reducing harmful reactive oxygen species and boosting beneficial gut bacteria. This suggests that mushroom polysaccharides could potentially be used to help cancer patients manage the immunosuppressive side effects of chemotherapy.