In 1976-1977, I adapted reversed-phase HPLC (RP-HPLC) to peptide and protein purification, starting with pituitary proteins and continuing with the first successful purification to homogeneity of human leukocyte interferon (IFN-alpha). Using this technology, I isolated and characterized 6-8 different leukocyte interferon subtypes, which were later identified as products of the IFN-alpha gene family. Since then, RP-HPLC became a standard procedure for isolation and analysis of proteins. The successful purification of IFN-alpha led to the development of Roferon-A, a drug used for the treatment of hairy cell leukemia, hepatitis C and a variety of other diseases. Later studies with my colleagues in Israel and abroad led to isolation and discovery of several cytokine receptors and binding proteins, including those of Type I IFNs, TNF and IL-18. The use of HPLC was indispensable in most of these studies.