Polychorinated biphenyl (PCB) congeners are a cause for concern due to their persistence in the environment, their lipophilic properties that cause them to bio-accumulate in top predators, and their adverse effects on mammalian health. For example, the common urogenital carcinoma reported in California sea lions (Zalophus californianus) (CSL) is associated with high tissue levels of PCBs, but the mechanisms responsible for this association are unknown. This study investigated the effect of exposure to six PCB congeners and a congener mix at low and environmentally relevant concentrations on NK cell-like and T cell activity using in vitro assays on cryopreserved lymph node mononuclear cells isolated from dead CSL. Non dioxin-like congeners 153 and 180 increased lymphocyte proliferation at 5 and 10 ppm, while congener 138 decreased proliferation by up to 43% at 15 ppm. Dioxin-like PCBs 118 and 169 did not affect lymphocyte proliferation, while the effects of congener 105 depended on the mitogen concentration; these did not correlate with their predicted toxic equivalent factors. NK cell-like activity was affected only by the highest concentration of PCBs tested; it was increased by non-dioxin-like congeners 138 and 153, and decreased by dioxin-like congener 169. The PCB congener mix suggested that the effects of PCB congeners were not simply additive. Our results concur with effects of PCBs reported for other pinniped's lymphocytes and add further experimental support to the observation that dioxin-like PCBs are not the most toxic congeners for marine mammals, contrary to effects in other species. This is the first evidence of in vitro suppression of NK cell-like cytotoxicity by a dioxin-like congener in a pinniped. More importantly, the observed results suggest that PCBs can modulate the CSL immune system, increasing exposed individuals’ susceptibility to viral and oncogenic challenges.

多氯联苯（PCB）同类物因其在环境中的持久性，亲油性（导致它们在顶级捕食者中生物蓄积）以及对哺乳动物健康的不利影响而备受关注。例如，在加利福尼亚海狮（Zalophus californianus）（CSL）中报告的常见泌尿生殖道癌与多氯联苯的高组织水平有关，但造成这种联系的机制尚不清楚。本研究调查曝光的效果六个PCB同类和同类物在低温和环境有关的浓度对NK细胞样细胞和T细胞活性的使用混合体外从死CSL中分离的冷冻保存的淋巴结单核细胞的检测分析。非二恶英样同源物153和180在5和10 ppm时增加了淋巴细胞的增殖，而同源物138在15 ppm时使增殖降低了43％。类二恶英的多氯联苯118和169不会影响淋巴细胞的增殖，而同类物105的作用取决于有丝分裂原的浓度。这些与他们预测的毒性当量因子没有关系。NK细胞样活性仅受最高浓度的多氯联苯影响。非二恶英类同系物138和153会增加它，而二恶英类同系物169会降低它。我们的结果与其他针扎式印刷电路板所报告的PCB效果一致。与其他物种的作用相反，二恶英样多氯联苯不是海洋哺乳动物毒性最高的同类物，这一观察结果为进一步研究提供了进一步的实验支持。这是第一个证据夹中二恶英样同源物在体外抑制NK细胞样细胞毒性。更重要的是，观察到的结果表明，多氯联苯可调节CSL免疫系统，增加暴露个体对病毒和致癌物质挑战的敏感性。