Nuclear Receptor Subfamily 4 Group A Member 1 Overexpression Prolongs Free Flap Allotransplant Graft Survival by Inducing T-Cell Anergy in the Rat.

[BACKGROUND] New strategies to inhibit acute rejection are needed for further applications of composite tissue allotransplantation. The nuclear receptor subfamily 4 group A member 1 (NR4A1) is considered a key controller of maintaining tolerance homeostasis. However, the effect of NR4A1 in suppressing rejection responses after allotransplantation remains unknown.

[METHODS] Brown Norway rat groin flaps were transplanted into Lewis rat recipients. The recipients were administrated cytosporone B, an NR4A1 activator. NR4A1 expression and graft survival time were assessed. T helper type 1 and regulatory T cell populations in the second lymphoid organ were detected by flow cytometry. Furthermore, a retrovirus containing NR4A1 was constructed and transfected to T cells in vitro. After stimulation, interleukin 2 and interferon gamma secretions were detected in the T cells.

[RESULTS] Administration of cytosporone B activated NR4A1 expression in allotransplant recipients and was associated with prolonged survival time of the vascularized free flap allograft. T helper type 1 cells in the recipient secondary lymphoid organs were decreased, whereas the population of regulatory T cells did not change. Interleukin 2 and interferon gamma were suppressed in vitro in the T cells overexpressing NR4A1.

[CONCLUSIONS] We demonstrated that the overexpressed NR4A1 is associated with suppressed graft rejection response. The suppression effect may attribute to induction of T-cell anergy and blockade of key immunologic cytokines.