Pavan Reddy, MD, University of Michigan Medical Center, Ann Arbor, MI, discusses a plenary presentation on oxygen sensing from the Transplantation & Cellular Therapy (TCT) 2021 virtual meeting presented by Nobel Laureate Prof. Gregg Semenza, and highlights how changes in oxygen concentration in the intestines influence the microbiome which is known to play a role in graft-versus-host disease. Dr Reddy moves on to discuss the ethics in the availability of CAR T-cell therapy as evaluated in sessions from the pediatric track of the Transplantation & Cellular Therapy (TCT) 2021 meeting. This interview took place during the Transplantation & Cellular Therapy (TCT) 2021 Meetings.