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.