Interferon regulatory factor 4 deficiency in CD8⁺ T cells abrogates terminal effector differentiation and promotes transplant acceptance

Abstract

Allogeneic CD8 + cytotoxic T cells play an essential role in rejecting transplanted allografts, but how their effector function is regulated on a transcriptional level remains unclear. Herein, we investigate the role of interferon regulatory factor 4 (IRF4) in controlling CD8 + T-cell function in response to transplant. B6.Rag1 À/À mice were adoptively transferred with CD8 + T cells isolated from either Irf4 fl/fl Cd4-Cre (T-cell-specific Irf4deficient) or Irf4 fl/fl control mice, followed by BALB/c skin transplantation. Recipients that received Irf4-deficient CD8 + T cells permanently accepted the skin allografts, whereas recipients that received control CD8 + T cells acutely rejected the transplanted skins. Mechanistically, compared with the transferred control CD8 + T cells in B6.Rag1 À/À recipients, the transferred Irf4-deficient CD8 + T cells lost the capacity to differentiate into CD127 À KLRG1 + terminal effector cells, barely produced effector cytokines and cytotoxic molecules (e.g. IL-2, IFN-c, TNF-a, granzyme A and granzyme B), and displayed defect in proliferative capacity, evident by their decreased Ki67 expression and lower frequencies. Moreover, the transferred Irf4-deficient CD8 + T cells displayed low expression of transcription factors ID2 and T-bet that govern the terminal effector T-cell programmes, and high expression of transcription factor TCF1 that maintains the na€ ıve-memory T-cell programmes. Hence, IRF4 deficiency in CD8 + T cells abrogates their terminal effector differentiation and promotes transplant acceptance. These findings suggest that targeting IRF4 expression represents an attractive and promising therapeutic approach for inducing transplant acceptance.

Ablation of BATF Alleviates Transplant Rejection via Abrogating the Effector Differentiation and Memory Responses of CD8+ T Cells

“…In the laboratory settings, WT B6 recipients reject the minor histocompatibility antigen-mismatched heart allografts, but CD8 + T cell-deficient recipients fail to do so ( 5 ). Moreover, we and others have demonstrated previously that lymphopenic mice reconstituted with CD8 + T cells alone acutely reject MHC fully mismatched allografts ( 6 , 7 ), suggesting that the adoptively transferred CD8 + T cells differentiate into cytotoxic effector T cells and sequentially drive the rejection of allografts in these lymphopenic recipients ( 7 ).…”

“…Recent studies have found that BATF and IRF4 cooperate to directly bind to and regulate gene expressions in T cells, such as Tcf7 and Tbx21 (encoding TCF1 and T-bet, respectively) ( 24 , 55 ). Of note, we have found previously that the deletion of IRF4 in T cells promotes transplant acceptance ( 21 ), and that IRF4-deficient CD8 + T cells fail to differentiate into effectors upon transfer into immunocompromised recipients ( 7 ). The cooperation between BATF and IRF4 appears to be essential in allogeneic T cell fate decisions.…”

“…As previously described ( 7 ), CD8 + T cells were isolated from the spleens and lymph nodes of WT or BATF –/– mice using the Dynabeads untouched mouse CD8 cells kit (Thermo Fisher Scientific). To obtain CD44 low naïve CD8 + T cells, the Depletion Dynabeads (Thermo Fisher Scientific) and Anti-CD44 mAb (clone IM7, Biolegend) were used to further purify the isolated CD8 + T cells.…”

“…As previously described ( 7 ), ~1.0 x 1.0 cm skin allografts from Balb/c mice were transplanted onto the backs of either WT B6 or B6. Rag1 –/– recipients.…”

“…For instance, transcription factors IRF4 ( 11 , 12 ), T-bet ( 13 ), ID2 ( 14 ), and ZEB2 ( 13 , 15 ) promote effector T cell differentiation, whereas TCF1 ( 16 ), ID3 ( 17 , 18 ), and BACH2 ( 19 ) restrain effector T cell differentiation and function. Of note, our recent works have demonstrated an essential role for IRF4, a pioneer factor induced by TCR signals ( 20 ), in terminal effector T cell differentiation and transplant rejection ( 7 , 21 ). However, the transcriptional programs that control the alloreactive CD8 + T cell responses remain poorly defined.…”