RecruitingPhase 2Drug trialPilot Trial of Fecal Microbiota Transplantation for Lymphoma Patients Receiving Axicabtagene Ciloleucel Therapy.To find out if adding treatment with fecal microbiota transplantation (FMT) is effective at treating gut-related side effects of antibiotic treatment in participants who are receiving standard therapy with anti-CD19 chimeric antigen receptor T-cell (CAR-T cell) therapy.