Abstract
The developing immune system is an adaptive system, primed by antigens, responsive to infectious pathogens, and can be affected by other aspects of the early rearing environment, including deviations from the normal provision of parental care. We investigated whether early rearing in an institutional setting, even when followed by years living in supportive and well-resourced families, would be associated with a persistent shift in T cell profiles. Immunophenotyping was used to enumerate CD4+ CD57+ and CD8+ CD57+ subsets, with gating strategies employed to differentiate naïve, central-memory, effector-memory, and terminally differentiated EM cells expressing CD45RA (TEMRA). Blood samples were collected from 96 adolescents, and PBMC isolated via Ficol gradient, followed by an optimized immunophenotypic characterization. CMV antibody titers were determined via ELISA. Adopted adolescents had lower CD4/CD8 ratios than did the control adolescents. Early rearing had a significant effect on the T cells, especially the CD8+ CD57+ CM, EM, and TEMRA cells and the CD4+ CD57+ EM cells. Adolescents who had spent their infancy in institutions before adoption were more likely to be seropositive for CMV, with higher antibody titers. CMV antibody titers were significantly correlated with the percentages of all CD8+ CD57+ cell subsets. In the statistical modeling, CMV antibody titer also completely mediated the relationship between institutional exposure and the ratio of CD4-to-CD8 cells, as well as the percentages of CD4+ CD57+ and CD8+ CD57+ subsets. These findings demonstrate that persistent immune differences are still evident even years after adoption by supportive American families. The shift in the T cells was associated with being a latent carrier of CMV and may reflect the role of specific T cell subsets in Herpes virus containment. In older adults, sustained CMV antigen persistence and immunoregulatory containment ultimately contributes to an accumulation of differentiated T cells with a decreased proliferative capacity and to immune senescence.