IL6 and cholangiocarcinoma: Our study adds a unique aspect to the literature on circulating levels of IL-6 as an immune marker of hepatobiliary pathology by showing that high levels of circulating IL-6 in plasma are not related to infection with O. viverrini, but to the development of the advanced and often lethal pathologies resulting from chronic O. viverrini infection: i.e., age and sex matched controls with O. viverrini infection and no pathology (APF- and CCA-) had undetectable levels of this inflammatory cytokine in their plasma.