Cytokines regulate the expression of specific sets of proteins which mediate their biological effects. We have comprehensively delineated the regulation of the human tryptophanyl-tRNA synthetase (hWRS) by eight different cytokines (including IFNs) and poly(I)·poly(C) in several cell lines. Six non-lymphoid cell lines were tested, and all of these produced human, IFN inducible hWRS (γ2) mRNA upon stimulation with IFN-γ. In all these cell lines the level of γ2 mRNA increased 2-4 h after induction reaching a stable plateau after 8-12 h. The IFN-γ induction of γ2 mRNA could be blocked by cycloheximide in human amniotic (AMA) cells, epithelial HeLa cells and HT1080 fibroblasts, but not in T98G glioblastoma cells. IFN-α and poly(I)·poly(C) elicited small, transient γ2 responses in a few of the non-lymphoid cell lines, whereas none of the other six cytokines tested elicited a response. The six lymphoid cell lines tested did not show the same induction pattern. In the monocytic cells, THP-1, γ2 mRNA was highly induced by IFN-γ, whereas in the B-cell fine, Daudi, γ2 mRNA was transiently induced by IFN-α and poly(I)·poly(C), and not by IFN-γ. Altered mRNA turnover rate as a consequence of IFN-γ treatment did not appear to play a significant role in the accumulation of γ2 transcript, since the stability essentially was the same in induced versus non-induced cells. We conclude that the hWRS gene is induced preferentially by IFN-γ, and that the induction pattern resembles the one reported for the IFN induced enzyme, indoleamine 2,3-dioxygenase (IDO).