AUTHOR=Haynes Laura TITLE=Aging of the Immune System: Research Challenges to Enhance the Health Span of Older Adults JOURNAL=Frontiers in Aging VOLUME=1 YEAR=2020 URL=https://www.frontiersin.org/journals/aging/articles/10.3389/fragi.2020.602108 DOI=10.3389/fragi.2020.602108 ISSN=2673-6217