text: In order to generate a molecular tool to discriminate between Interleukin-6 classic signaling and Interleukin-6 trans-signaling, a cDNA coding for human Interleukin-6 and a cDNA coding for the human soluble Interleukin-6 receptor were connected by a cDNA coding for a 13 amino acids long linker, which was long enough to bridge the 40 Å distance between the COOH terminus of the soluble Interleukin-6 receptor and the NH2 terminus of human Interleukin-6. The generated cDNA was expressed in yeast cells and in mammalian cells and it was shown that.