**Abstract**

IL-6 is a pleiotropic cytokine produced in response to tissue damage and infections. This up-regulation was observed during infection with a highly virulent VSV strain. There was potential association between IL-6 levels and virus virulence. In this chapter we would like to explore in more detail the biological functions of IL-6 in different virus models. We also discuss the debatable role of IL-6 during viral infections. Previous studies show the potential role of IL-6 to mount a proper immune response during some viral infections, others link this cytokine with exacerbation of viral disease. These latter findings lend support to the hypothesis that up-regulation of IL-6 during certain viral infections may promote virus survival and/or exacerbation of clinical disease. Previous experimental evidences also suggest potential negative consequences that increased levels of IL-6 might have on the cellular immune response against viruses.

**Keywords:** RNA virus-IL6-soluble-imune-host
