In utero arsenic exposure and fetal immune repertoire in a US pregnancy cohort

• In utero arsenic exposure related to altered lymphocyte profiles in newborns
• Higher arsenic exposure associated with a decrease in naïve activated T cells
• Higher arsenic exposure also related to an increase in activated Th2 cells
• Further, placental AQP9 expression correlated with  IL1β expression.

Arsenic has wide-ranging effects on human health and there is evidence that it alters the immune response by influencing CD4 +/CD8 + T cell ratios, IL-2 cytokine levels, and the expression of immune-response genes. We investigated the impact of in utero environmental arsenic exposure on immune development and function in newborns participating in a pregnancy cohort in New Hampshire, U.S., where arsenic levels have exceeded the current EPA maximum contaminant level of 10 μg/L. Our results showed that maternal urinary arsenic concentrations were inversely related to absolute total CD45RA + CD4 + cord blood CD69 + T cell counts (N = 116, p = 0.04) and positively associated with CD45RA + CD69 − CD294 + cell counts (p = 0.01). In placental samples (N = 70), higher in utero urinary arsenic concentrations were positively associated with the expression of IL1β (p = 0.03). These data provide evidence that relatively low-level arsenic exposure in utero may alter the fetal immune system and lead to immune dysregulation.