Arnér is an MD PhD and received his degrees from Karolinska Institutet in Stockholm, Sweden. In his early work he studied nucleotide metabolism and the biochemistry of nucloside analogs used as anticancer or antiviral drugs. Later he moved to studies of redox biochemistry, with a focus on the mammalian thioredoxin system and selenoprotein synthesis and function. With that field of interest, he first worked with Arne Holmgren, Stockholm, and then August Böck, Munich, before establishing his own line of research back at Karolinska Institutet, where he is now head of the biochemistry division, in the department of medical biochemistry and biophysics. He has served as dean of postgraduate education at Karolinska Institutet and he was Editor of BBA General Subjects for some years before becoming Executive Editor in 2008.