Polychlorinated biphenyl mixtures (Aroclors) inhibit LPS-induced murine splenocyte proliferation in vitro

The immune system is believed to be a sensitive indicator for adverse polyc hlorinated biphenyl (PCB)-induced health effects. Four commercial PCB mixtu res (Aroclors) or six individual PCB congeners were evaluated for their eff ect on splenocyte viability and lipopolysaccharide (LPS)-induced splenocyte proliferation in vitro in two strains of mice, C57B1/6 (high affinity arom atic hydrocarbon receptor (AhR) complex) and DBA/J (low affinity AhR comple x). All four Aroclors, the selected individual noncoplanar congeners, or tw o tertiary mixtures containing one congener from each class significantly d ecreased the in vitro LPS-induced proliferation of murine splenocytes in ei ther strain of mice without inducing a significant decrease in viability. I n contrast, selected individual coplanar or mono-ortho-coplanar congeners d id not inhibit splenocyte proliferation or viability at any concentration. These results suggest that mixtures of PCBs and/or congener class (specific ally, noncoplanar congeners) may be more highly immunotoxic than individual planar and mono-ortho-coplanar congeners alone. Thus, this in vitro assay has revealed a more complex pattern of immunotoxicity of Aroclors versus in dividual congeners than has previously been reported or anticipated based o n both in vivo derived immunotoxic data and standard comparisons to 2,3,7,8 -tetrachlorodibenzo-p-dioxin (TCDD). These results have important practical significance since mixtures of PCB congeners were used industrially and no w contaminate the environment. (C) 1999 Elsevier Science Ireland Ltd. All r ights reserved.