In utero per - and polyfluoroalkyl substances (PFAS) exposure and changes in infant T helper cell development among UPSIDE-ECHO cohort participants.

Background: Environmental exposures to toxicants, such as per- and polyfluoroalkyl substances (PFAS), during gestation can disrupt immune development, causing long-term impacts on a child's ability to generate a well-regulated, protective immune response. T-cells coordinate with all immune cell types to orchestrate both cellular and antibody-mediated responses. While there is compelling evidence that PFAS alters immunity in humans, the specific effects of early life PFAS exposure on infant T-cell development are unreported. Because of their central role in immunity, altered T-cell development in infants would have implications on immune responses broadly and long-term.

Objectives: We seek to model longitudinal changes in the frequency of functionally distinct CD4+ T-cell subpopulations from birth through 12 months and their association with in-utero PFAS exposure.

Methods: Maternal-infant dyads were recruited as part of the UPSIDE-ECHO cohort during the first trimester between 2015 and 2019 in Rochester, New York; dyads were followed through the infant's first birthday. Maternal PFAS concentrations (PFOS, PFOA, PFNA, PFHXS and PFDA) were quantified in serum during the second trimester using high-performance liquid chromatography and tandem mass spectrometry. Infant lymphocyte frequencies were assessed at birth, 6- and 12-months using mass cytometry and high-dimensional clustering methods. Linear mixed-effects models were employed to analyze the relationship between maternal PFAS concentrations and CD4+ T-cell subpopulations (n=200). All models included a PFAS and age interaction and were adjusted for parity, infant sex, and pre-pregnancy body mass index.

Results: In-utero PFAS exposure correlated with multiple CD4+ T-cell subpopulations in infants. The greatest effect sizes were seen in T-follicular helper (Tfh) and T-helper 2 (Th2) cells at 12 months. A log-unit increase in PFOS was associated with lower Tfh [0.17% (95%CI: -0.30, -0.40)] and greater Th2 [0.27% (95%CI: 0.18, 0.35)] cell percentages at 12 months. Similar trends were observed for PFOA, PFNA, PFHXS and PFDA. TEXT.

Discussion: Maternal PFAS exposures correlate with cell-specific changes in the infant T-cell compartment, including key CD4+ T-cell subpopulations that play central roles in coordinating well-regulated, protective immunity. Future studies into the role of PFAS-associated T-cell distribution and risk of adverse immune-related health outcomes in children are warranted. https://doi.org/10.1289/EHP16726.