AUTHOR=Hayashi Robert J. TITLE=Editorial: Immunological Challenges Following Pediatric Hematopoietic Transplantation JOURNAL=Frontiers in Immunology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.732261 DOI=10.3389/fimmu.2021.732261 ISSN=1664-3224