The purpose of NOT-HL-23-116 is to further elucidate mechanisms underlying the life-threatening pulmonary complications that ensue after hematopoietic stem cell transplantation (HCT) in all age groups. This reissue of NOT-HL-20-761 expands the scope of the science to include children and adults, autologous transplant recipients, innovative technologies including device development, and mechanistic clinical trials in children and adults.