A TNF-.alpha. binding polypeptide is provided, which is related to a domain of staphylococcal protein A (SPA) in that the sequence of the polypeptide corresponds to the sequence of the SPA domain having 1 to about 20 substitution mutations. Nucleic acid encoding the polypeptide, expression vector comprising the nucleic acid, and host cell comprising the expression vector are also provided. Also provided are methods comprising a step of affinity separation or detection, in which step a polypeptide according to the invention is used. Such methods may be used for reducing the content of TNF-.alpha. in a body fluid.