The properties of 3d, 4d, and 5d transition-metal elements in ?-Fe have been studied using ab initio density-functional theory. The intrinsic properties of the solutes have been characterized as well as their interaction with point defects. Vacancies and interstitials of (110) and (111) orientations have been considered in order to discern trends that may explain experimental evidence of solute influences on radiation response and possibly aid future material design regarding the choice of alloy composition. Depending on the solute element, the different interactions are governed by the chemical interactions and the solute size factor. It is shown that magnetic interactions play an important role for the properties of the center series 3d elements, especially so for the antiferromagnetically coupling V, Cr, and Mn. For the 4d, 5d, and remaining 3d elements the interaction with point defects is mainly governed by the solute size factor. The solute-solute interaction is mostly repulsive with a few exceptions. The interactions with vacancies are in most cases binding; but the second nearest neighbor configurations exhibit strong repulsion for the early transition metals. Cr and Mn interact strongly binding with interstitial defects. The trends of the solute defect interactions have been determined to depend on the characteristic local deformation. Early transition metals interact stronger with defects than late ones of equal size factor.