Preface [Hot topic: Ribosome-Inactivating Proteins Executive Editor: Fiorenzo Stirpe ]

To be invited to edit a special issue on a field of the editor's choice was an honour, and an even greater one came when some of the best scientists working on ribosome-inactivating proteins consented to contribute. But perhaps the greatest satisfaction for me was to realize how much progress has been done in a field to which our laboratory contributed from the very beginning of the modern studies, in the seventies. Scientists should always look to the future, but I must admit that when we started working on ricin I could not possibly dream of such a development. In thirty years we saw that the number of potent toxins grew from two, ricin and abrin, to six, that single-chain ribosomeinactivating proteins (RIPs) were found, and that non-toxic two-chain RIPs were identified. In other words, a whole class of proteins was defined. We also saw the development of research aimed to find useful applications of RIPs. The bulk of this was on the conjugates of RIPs with carriers, mainly antibodies to form “immunotoxins”, which could deliver them in a selective manner to cells to be eliminated. The “magic bullet” envisaged several decades before by the genius of Paul Ehrlich seemed at hand, and in a sense it was obtained, in that immunotoxins have been done and work, although their use in medicine is not yet practicable. They are, however, excellent experimental tools, as it is demonstrated by their use in neurology, although their potential has not yet been fully realised. Also interesting are the possible applications of RIPs for their antiviral properties. Attempts have been, and still are done, to utilise these proteins not only to improve plant resistance to viral infection, but also to combat human viral diseases. So far full success has not been achieved, but the results are promising. Sadly, we also heard of the possible use of ricin as a biological weapon, but fortunately the fears did not materialize. However, the greatest importance of RIPs is their very existence, and a great challenge will be to understand the role in Nature of these proteins. Proteins are expensive to make, and the widespread conservation of RIPs in plants, in at least one bacterium, and possibly in animals suggests they must have an important role in the producing organisms. Finally, one wonders what have been the economical consequences of the discovery of RIPs. They are definitely minuscule as compared to those of mass-produced goods, however, they are in the catalogues of several suppliers, an industry was created and people were employed. In a time when the emphasis is on research giving immediate economic returns, this is another example, although modest, of the consequences of “basic” research, born out of the “scientific curiosity” of few scientists. Last but not least, I wish to express my gratitude to the Editors who assigned me the task of editing this special issue, and to all authors of the reviews. It was a great pleasure to renew long-time friendships and to make new ones.