Ablation of Transcription Factor IRF4 Promotes Transplant Acceptance by Driving Allogenic CD4+ T Cell Dysfunction

Abstract

CD4 T cells orchestrate immune responses and destruction of allogeneic organ transplants, but how this process is regulated on a transcriptional level remains unclear. Here, we demonstrated that interferon regulatory factor 4 (IRF4) was a key transcriptional determinant controlling T cell responses during transplantation. IRF4 deletion in mice resulted in progressive establishment of CD4 T cell dysfunction and long-term allograft survival. Mechanistically, IRF4 repressed PD-1, Helios, and other molecules associated with T cell dysfunction. In the absence of IRF4, chromatin accessibility and binding of Helios at PD-1 cis-regulatory elements were increased, resulting in enhanced PD-1 expression and CD4 T cell dysfunction. The dysfunctional state of Irf4-deficient T cells was initially reversible by PD-1 ligand blockade, but it progressively developed into an irreversible state. Hence, IRF4 controls a core regulatory circuit of CD4 T cell dysfunction, and targeting IRF4 represents a potential therapeutic strategy for achieving transplant acceptance.

Ablation of interferon regulatory factor 4 in T cells induces “memory” of transplant tolerance that is irreversible by immune checkpoint blockade

“…Cd4 ‐Cre, Irf4 flox/flox , B6.SJL CD45.1 congenic, TEa TCR transgenic, 8 BALB/c, and C57BL/6 (B6) mice were purchased from Jackson Laboratory (Bar Harbor, MA). Irf4 flox/flox mice were crossed to Cd4 ‐Cre mice to create Irf4 fl/fl Cd4 ‐Cre mice.…”

“…8 Some recipient mice were ip injected with 400 μg Rat IgG, or 200 μg anti‐PD‐L1 (clone 10F.9G2) plus 200 μg anti-CTLA‐4 (clone 9D9) mAbs (Bio‐X‐Cell, West Lebanon, NH) on days 0, 3, 5 post‐heart grafting.…”

“…Irf4 −/− CD4 + T cells were activated for 3 days with BALB/c splenic DCs and 100 IU IL‐2 (PeproTech, Rocky Hill, NJ), and then transduced with IRF4‐GFP or GFP‐Ctrl retrovirus as previously described. 8 Cells were cultured for 1 day after transduction, and then adoptively transferred into Irf4 fl/fl Cd4‐Cre mice on day 1 post‐heart transplantation.…”

“…All heart allografts were acutely rejected due to checkpoint blockade‐mediated reinvigoration of Irf4 −/− T cells. 8 Strikingly, those Irf4 fl/fl Cd4 ‐Cre recipients with rejected heart allografts still permanently accepted the subsequent donor‐type skin grafts, indicating that checkpoint blockade‐reinvigorated alloreactive Irf4 −/− T cells become re‐dysfunction within 30 days. Indeed, initial checkpoint blockade did not restore cell frequency, effector memory cell generation, and IFN‐γ/TNF‐α production of alloreactive Irf4 −/− T cells at day 30 post‐heart grafting.…”

“…The dysfunctional state of Irf4 −/− T cells was initially reversible by blocking programmed death‐ligand 1 (PD‐L1) and cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4), but it progressively developed into a terminal/irreversible dysfunctional state. 8 Therefore, the TCR‐IRF4 axis governs the functional versus dysfunctional fates of alloreactive T cells.…”