This trial is conducted in Europe. The aim of this trial is to investigate the safety, tolerability, pharmacokinetic (the effect of the body on the investigated drug), pharmacodynamic biomarkers (biomarkers related to anti-IL-21 expected mode of action) and signs of clinical efficacy of increasing single doses, at 9 i.v. (into the vein) dose levels in Healthy Subjects , at 3 i.v. dose levels in subjects with rheumatoid arthritis (RA) and at 3 s.c. dose levels in Healthy Subjects.