IL6ST and systemic inflammatory response syndrome: The binding affinity of IL-6 to sIL-6R is ~1 nM; thus, extreme elevation of serum IL-6 level observed in severe SIRS and CRS can lead to the formation of a complex between IL-6 and sIL-6R in the serum, resulting in systemic inflammation through the activation of gp130-expressing cells, particularly vascular endothelial cells (22).