Soluble FGL2 induced by tumor necrosis factor-α and interferon-γ in CD4+ T cells through MAPK pathway in human renal allograft acute rejection

Background: Acute rejection (AR), initiated by alloreactive CD4(+) T cells, hampers allograft survival. Soluble fibrinogen-like protein 2 (sFGL2) is a novel effector of CD4(+) T cells. We previously found that serum sFGL2 significantly increased in renal allograft recipients with AR. In this study, sFGL2 secretion by CD4(+) T cells and its mechanism were further explored both in vivo and in vitro. Materials and methods: Forty cases of living-related renal transplant recipients with biopsy-proven AR or stable renal function were collected and detected serum sFGL2, tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma, and peripheral CD4(+) T cells. In vitro, the isolated human CD4(+) T cells were stimulated by TNF-alpha or IFN-gamma. sFGL2 in the supernatant and mitogen-activated protein kinase (MAPK) proteins in the CD4(+) T cells were investigated. Approval for this study was obtained from the Ethics Committee of Fudan University. Results: sFGL2, TNF-alpha, IFN-gamma, and CD4(+) T cells were significantly increased in the peripheral blood of renal allograft recipients with AR. Stimulation with 1000 U/mL TNF-alpha or 62.5 U/mL IFN-gamma for 48 h provided an optimal condition for CD4(+) T cells to secrete sFGL2 in vitro. Phosphorylated (p-) c-Jun N-terminal kinase was remarkably upregulated in the activated CD4(+) T cells, whereas no significant changes were found in p-p38 MAPK or p-ERK1/2 expression. Furthermore, inhibition of c-Jun N-terminal kinase significantly reduced sFGL2 secretion by CD4(+) T cells. Conclusions: sFGL2 secretion by CD4(+) T cells can be induced with TNF-alpha and IFN-gamma stimulation through MAPK signaling in renal allograft AR. Our study suggests that sFGL2 is a potential mediator in the pathogenesis of allograft rejection. (C) 2013 Elsevier Inc. All rights reserved.