Associations of maternal immune response and MeHg exposure at 28 weeks gestation in the Seychelles Child Development Study: Methylmercury, PUFA and pregnancy immune function

Problem: Maternal methylmercury (MeHg) exposure may be associated with immune response during pregnancy. Method of study: In the high fish‐eating Seychelles Child Development Study Nutrition Cohort 2, we examined the association between maternal MeHg, polyunsaturated fatty acids (PUFA), and immune markers (Th1:Th2; TNF‐α, IL‐1β, IFN‐γ, IL‐2, IL‐4, IL‐5, IL‐10, MCP‐1, TARC, sFlt‐1, VEGF‐D, CRP and IL‐6) at 28 weeks’ gestation. Linear regression examined associations between MeHg exposure and immune markers with and without adjustment for PUFA. Results: In all models, as MeHg concentrations increased, the Th1:Th2 ratio, total Th1 and individual Th1 (IL‐1β, IL‐2, TNF‐α) concentrations decreased. MeHg was not associated with total Th2 cytokines but was associated with a decrease in IL‐4 and IL‐10. MeHg was positively associated with TARC and VEGF‐D and negatively associated with CRP. There was a significant interaction between MeHg and the n‐6:n‐3 ratio, with MeHg associated with a larger decrease in Th1:Th2 at higher n‐6:n‐3 PUFA ratios. The n‐3 PUFA were associated with lower CRP, IL‐4 and higher IFN‐γ. The n‐6 PUFA were associated with higher IL‐1β, IL‐2, TNF‐α, IL‐4, IL‐10, CRP and IL‐6. Conclusion:Maternal MeHg was associated with markers of immune function at 28 weeks’ gestation. A significant interaction between MeHg and the n‐6:n‐3 ratio on the Th1:Th2 ratio suggests that the n‐3 PUFA may mitigate any immunosuppressive associations of MeHg. The n‐3 and n‐6 PUFA were associated with suppressive and stimulatory immune responses, respectively. Overall, the associations were of small magnitude, and further research is required to determine the clinical significance.