Chemokines (e.g., IL-8) were originally identified as chemotactic proteins obtained from different natural sources. These were purified by the use of a bioassay followed by N-terminal sequencing and then molecular cloning giving the full sequence and making it possible to express the chemokine as a recombinant protein. In this way we were sure that the biologically active chemokine is really released from natural sources. Today, using the genome walking strategy, we have discovered an ever-increasing number of novel genes encoding chemokines that were expressed in bacteria or eukaryotic cells and subsequently tested as the recombinant form for its biological activity.