Replacement therapy of fetal thymus

Objective To investigate whether the allogeneic thymus transplantation can be a method to cure the deficiency of the T-cells. Methods In this study, a murine thymus excision model was developed to receive an intra-species embryonic thymus transplantation.The mice were divided into three groups with 10 animals per group.The first group was normal mice that served as the control group.The second group is the thymectomy-only model which served as control group.The third group received the embryonic thymus transplantation.Total T-cell counts and the number of T-cells per unit weight of the mice in these three groups were determined.Additionally, T-cell subsets were detected by flow cytometry, using the number of CD3+ CD4+ double-positives to determine helper T-cells(Th), CD3+ CD8+ double-positives to determine the cytotoxic T-cells(Tc), and CD4+ CD25+ foxp3 triple-positive cells to determine the regulatory T cells(Tregs)content.A new simplified method was used to determine the T-cell receptor excision circles(TRECs)from tissues. Results The number of surviving mice in each group were nine for controls; eight for embryonic thymus transplant recipients; and eight for thymectomy alone.The T thymocyte count results showed that the total and mean value of T lymphocytes between the three groups were significantly different(P<0.05)and the datas are(16.24±2.98)×107、(4.58±1.29)×107、(9.92±2.24)×107 and (7.53±1.35)×106、(2.38±0.66)×106、(5.23±1.10)×106.For all T lymphocyte subsets analyzed, the datas of Th were (7.19±0.38)%、(1.51±0.37)%、(3.33±0.40)%; the datas of Tc were(7.21±0.41)%、(1.31±0.32)%、(3.41±0.48)%; and the datas of Tregs were(2.17±0.21)%、(0.48±0.12)%、(1.12±0.12)%.Statistical analyses demonstrated that there were significantly different in Th, Tc and Treg lymphocytes in each group(P< 0.05). Statistical analyses showed that these three groups were significantly different(P<0.05)in TRECs.Control mice(17.04±1.69)had the highest content of TRECs and mice with embryonic thymus transplant(12.45±1.51)had fewer TRECs than the control mice but more than the mice with thymectomy(9.53±0.84). Conclusion This study demonstrated that embryonic thymus transplantation can improve cellular immune function, confirming that the embryonic thymus can restore myriad T-cell lineages. Key words: Thymectomy; Immune; Fetal thymus; Transplantation