The finding that the two tumor necrosis factor receptors (TNFR) exist in soluble form in various body fluids not only has substantiated the paradigm of naturally existing soluble cytokine receptors but also has represented a milestone on the road to the biochemical and biological characterization of the two TNFRs. This chapter gives a simple, basic protocol for the purification of the two soluble TNFRs. The protocols found here may be easily adapted for the purification of various other soluble cytokine receptors. The purified proteins may be used in biological experiments or for the generation of specific research tools such as polyclonal or monoclonal antibodies.
