The dynamic changes of T-bet(+)/GATA-3(+) and RORgammat(+)/FOXP3(+) cells in recipient spleens and grafts after rat orthotopic liver transplantation

Abstract

Background: Rejection of transplanted liver occurs when the host generates alloantigen-reactive T cells, and CD4(+) T-cell subsets, including Th1, Th2, T17 and iTreg, could be involved in changing the dynamics of graft rejection onset. In the current immunosuppressive strategies, rejection is treated as an undifferentiated process that is uniform, which results in the failure of tolerance induction. Here, we established a rejection model to observe the reciprocal interaction of CD4(+) T-cell subsets in the complex networks of the immune system.

Methods: Orthotopic liver transplantation (OLT) from male inbred Lewis rats (n=15) to male inbred Brown Norway (BN) rats was performed by Kamada's two-cuff technique without reconstruction of the hepatic artery. OLT from BN to BN rats (n=5) was performed as a control. Recipients were sacrificed on postoperative days 3, 5, 7, 9, 11, 13 and 15. Recipient spleens and grafts were harvested, fixed in 10% neutral formalin, and embedded in paraffin. Meanwhile, hematoxylin and eosin and immunohistochemical staining was done, acute rejection was graded by the Banff scheme, and the number of T-bet(+), GATA-3(+), RORgammat(+) and FOXP3(+) cells in the spleen and grafts were counted.

Results: In recipient spleens, the T-bet(+) and RORgammat(+) cells were increased more significantly in the mild acute rejection (AR) group than in the control group (P=0.016, P=0.009, respectively), while both cell types were decreased in the moderate AR group. Compared with the control group, the RORgammat(+) cells did not differ significantly in the severe AR group, while the T-bet(+) cells were significantly decreased (P=0.465, P=0.009, respectively). The GATA-3(+) cells were significantly decreased in the mild AR group compared with the control group (P=0.009). With regard to the FOXP3(+) cells, there was no significant difference between the control and mild AR groups (P=0.754), while they were significantly decreased in the moderate and severe AR groups (P=0.028, P=0.009, respectively). The ratio of T-bet(+)/GATA-3(+) cells was more associated with AR than was the RORgammat(+)/FOXP3(+) cell ratio in the early stage. In the graft, the T-bet(+) and RORgammat(+) cells were significantly increased in mild, moderate and severe AR groups compared with the control group (P<0.009). The expression of GATA-3(+) cell was not significantly increased in the mild AR group compared with the control group, while it was significantly increased in the moderate and severe AR groups (P=0.028, P=0.009, respectively). Concerning the FOXP3(+) cells, no significant difference was found between the control and mild AR groups (P=0.347), while they were significantly increased in the moderate and severe AR groups (P<0.009).

Conclusions: Our study revealed the dynamic changes of T-bet(+), GATA-3(+), RORgammat(+) and FOXP3(+) cells in the spleen and grafts of recipient rats. It seems that the ratio of T-bet(+)/GATA-3(+) cells was more associated with AR than was RORgammat(+)/FOXP3(+) cells in the early stage of rejection, while the ratio of RORgammat(+)/FOXP3(+) cells was associated more with the later but more persistent stage of rejection. This study could make a contribution to the optimal selection of immunosuppressive regimens according to the dynamic changes in CD4(+) T-cell subsets at different stages of rejection.