Hobit and human effector T-cell differentiation: The beginning of a long journey.

Besides growing plants, eating a lot, and drinking beer, Tolkien's Hobbits enjoy maintaining a quiet state. Regarding the latter, the name chosen for a recently discovered transcription factor seems to be unintentionally appropriate. The zinc finger protein ZNF683 was originally named "Hobit" for Homolog of Blimp-1 in T cells. In this issue of the European Journal of Immunology, Braga et al. [Eur. J. Immunol. 2015. 45: 2945-2958] demonstrate that in humans, Hobit is almost exclusively expressed in effector T cells, in particular in quiescent and long-lived effector-type CD8(+) T cells. Hobit may initially appear as another "player" in the quest for transcription factors guiding T-cell differentiation; the discoveries of T-bet, Eomes, Blimp-1, and others have significantly contributed to our understanding of how this process is tightly regulated. However, Hobit may be special--the currently available results suggest substantial differences in Hobit's regulatory functions between mice and humans, such as expression patterns and IFN-γ regulation. And it may turn out that Hobit's function in human T cells is highly adapted to lifelong, periodic challenges with varying, physiological doses of pathogens. Thus, the new study about Hobit in human T cells may be the beginning of a long journey.