- Deficiency in the transcription factor interferon regulatory factor (IRF)-2 leads to severely compromised development of natural killer and T helper type 1 cells. Lohoff, M., Duncan, G.S., Ferrick, D., Mittrücker, H.W., Bischof, S., Prechtl, S., Röllinghoff, M., Schmitt, E., Pahl, A., Mak, T.W. J. Exp. Med. (2000)