The anatomical and functional study of the thymus - defining the milestones of the thymic aging in the elderly human population

This project is an anatomical and functional study of the human thymus focused on defining milestones of thymic aging in the elderly population. The work addresses a central hypothesis that residual thymic function persists in some individuals until the end of life and that identifying structural and molecular correlates of such persistence can improve understanding of age-related changes in human immunity. To overcome historical barriers—scarcity of human tissue from very old individuals and a lack of standardized markers of thymic cellular activity in advanced age—a cohort at the Kentucky College of Osteopathic Medicine (KYCOM) spanning ages roughly 50 to over 100 years was developed by the researchers. Using this cohort, the team applies integrated approaches including immunocytochemistry, gene expression profiling, and careful postmortem anatomical evaluation to characterize thymic structure, cellular composition, and molecular signatures across advanced ages.

Key empirical observations from the KYCOM cohort include the discovery that a subset of elderly individuals retain structurally and functionally preserved thymic tissue at death. The team documented cases of unilateral thymic involution in very advanced age, where one thymic lobe maintains medullary and cortical antigen expression and CD3+ cells, preserving functional integrity despite degeneration of the contralateral lobe. The investigators also identified specific anatomical parameters that appear characteristic of this elderly age group, and they observed associations between body mass and thymic structure and function. Comparative gene expression analyses reveal that genes mediating thymic function in young humans are expressed in some elderly individuals as well, suggesting molecular preservation of functional programs in a fraction of the aged population.

Building on these findings, the study aims to determine whether protein products of the identified genes can serve as reliable molecular markers of late-life thymic function. Establishing such markers would permit standardized assessment of thymic activity in elderly individuals and support further studies of how preserved thymic function influences immune competence, vaccine responsiveness, and susceptibility to infection and disease in old age. The research team integrates expertise from gross anatomy and immunology at KYCOM and includes student fellows contributing to tissue collection, histological and immunocytochemical assays, and molecular profiling.

The project’s contribution is twofold: it fills a critical gap in human thymus aging research by providing systematic anatomical and molecular data from a well-characterized elderly cohort, and it proposes actionable biomarkers for detecting residual thymic function in late life. The findings have potential translational implications for gerontology and clinical immunology, informing strategies that might preserve or augment thymic function or tailor interventions to individuals with retained thymic capacity. Funded via NIH support (R15-AG078992), this research advances understanding of how thymic involution unfolds in humans and seeks to define milestones of thymic aging that can guide future basic and clinical investigations.