Initiates signal transduction through binding to interleukin-6 receptor subunit beta IL6ST, independently of the cognate IL6 receptor IL6R. In infected primary effusion lymphoma cells, promotes proliferation of cells, protects them from apoptosis, and promotes immune evasion of interferon activity. Drives also blood to lymphatic endothelial cell differentiation. Interacts with host IL6ST. Belongs to the IL-6 superfamily.