T cell specific deletion of IRF4 with Ox40-Cre impairs effector and memory T cell responses in heart transplantation

Abstract

Background: IRF4 is the pioneer factor for effector T cell maturation. Here we investigated the function of IRF4 in maintaining OX40-related T cell responses following alloantigen activation in a mouse heart transplantation model.

Methods: Irf4^flox/flox mice were bred with Ox40^cre/+ mice to generate Irf4^flox/floxOx40^cre/+ mice. Wild type C57BL/6, Irf4^flox/floxOx40^cre/+ mice were transplanted with BALB/c heart allografts, with or without BALB/c skin-sensitization. CD4⁺ TEa T cells co-transfer experiments and flow cytometric analysis were conducted to investigate the amount of CD4⁺ T cells and the percentage of the T effector subset.

Results: Irf4^flox/floxOx40^cre/+ and Irf4^flox/floxOx40^cre/+ TEa mice were constructed successfully. IRF4 ablation in activated OX40-mediated alloantigen specific CD4⁺ TEa T cells reduced effector T cell differentiation (CD44^hiCD62L^lo, Ki67, IFN-γ), which caused long-term allograft survival (> 100 d) in the chronic rejection model. In the donor skin-sensitized heart transplantation model, the formation and function of alloantigen-specific memory CD4⁺ TEa cells were also impaired in Irf4^flox/floxOx40^cre/+ mice. Additionally, deletion of IRF4 after T cell activation in Irf4^flox/floxOx40^cre/+ mice reduced T cell reactivation in vitro.

Conclusions: IRF4 ablation after OX40-related T cell activation could reduce effector and memory T cell formation and inhibit their function in response to alloantigen stimulation. These findings could have significant implications in targeting activated T cells to induce transplant tolerance.

Keywords: Heart transplantation; T cell differentiation; Transplant tolerance; Transplantantion immunity.