The microstructure of materials and its evolution are influenced by the interaction of point defects with the solute atoms, already present or introduced by irradiation. Electronic structure calculations are nowadays intensively used to characterise these interactions. Prediction of the consequences of these interactions on the microstructure evolution, for instance on the diffusion properties, can be obtained from raw first principles data or more often, by introducing these data in higher scale models. This paper reviews the current knowledge, gained from recent intensive sets of first principles calculations, of the interactions between point defects (vacancies and self interstitial atoms) in Fe and W matrix, and solute elements, both substitutional (mostly 3d, 4d and 5d transition metals) and interstitial (C, N, H and He).