Allorecognition in Hydractinia, a cnidarian, is governed by two different, highly polymorphic genes encoding transmembrane proteins. Using a fluorescent cell read-out system, a new study now shows that the basis for specificity involves homophilic interactions between extracellular domains.

This report describes a method of preparing samples of phosphodiesterase suitable for some chemical studies of desoxyribonucleic acid. A study of the use of purified phosphodiesterase in hydrolyzing thymonucleic acid has already been made (1). The source of our phosphodiesterase (snake venoms) was suggested by the work of Gulland and Jackson (2), although it now seems to us that their conclusio...