Control of CD8+ T cell proliferation by the transcription factor ELF4

Transcription factors that regulate quiescence, proliferation, and homing of lymphocytes are critical for effective immune system function. In the present study, we demonstrated that the transcription factor ELF4 directly activates the tumor suppressor KLF4 downstream of T cell receptor (TCR) signaling to induce cell cycle arrest in naïve CD8+ T cells. Elf4- and Klf4-deficient mice accumulated CD8+CD44hi T cells during steady-state conditions and generated more memory T cells after immunization. The homeostatic expansion of CD8+CD44hi T cells in Elf4-null mice resulted in a redistribution of cells to non-lymphoid tissue due to reduced expression of the transcription factor KLF2, and the surface proteins CCR7 and CD62L. This work describes the combinatorial role of lymphocyte-intrinsic factors in the control of T cell homeostasis, activation and homing. CD8 T cells were purified from spleen of wild type and Elf4-/- mice and CD8 T cells were left untreated or activated in vitro by culturing on anti-CD3 coated plates and anti-CD28 in media (RPMI 10% FBS supplemented with 5% T-stim) for 3.5 days. RNAs isolated from wild type and Elf4 -/- CD8+ T cells were used in Affimetrix oligonucleotide arrays either untreated or after 3.5 days of activation.