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Homeostatic properties and phenotypic maturation of murine CD4+ pre-thymic emigrants in the thymus.

Dong J, Chen Y, Xu X, Jin R, Teng F, Yan F, Tang H, Li P, Sun X, Li Y, Wu H, Zhang Y, Ge Q - PLoS ONE (2013)

Bottom Line: Qa2, the expression of which indicates the phenotypic maturation of SPs and RTEs, was found to be upregulated in CD4(+) pre-RTEs in thymic perivascular space.Migratory dendritic cells that surround this region contribute to Qa2 expression in pre-RTEs.The dendritic cell-driven Qa2 induction of CD4(+) pre-RTEs is independent of MHC class II and Aire molecules.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Medical Immunology, Ministry of Health, Department of Immunology, Peking University Health Science Center, Beijing, China.

ABSTRACT
After a tightly regulated developmental program in the thymus, "mature" single positive (SP) thymocytes leave the thymus and enter the periphery. These newly arrived recent thymic emigrants (RTEs) are phenotypically and functionally immature, and will complete a dynamic maturation in the peripheral lymphoid organs before being licensed to be resident naïve T cells. To study the early events occurring in the RTE maturation process, we identified the phenotype of CD4(+) pre-RTEs, a population of CD4(+) SP thymocytes that have acquired the thymus egress capability. Compared to peripheral naïve T cells, CD4(+) pre-RTEs displayed superior survival capability in lymphoreplete mice and faster proliferation under lymphopenic condition. The differences in Bcl2/Bim expression and/or heightened IL-7 signaling pathway may account for the pre-RTEs' better responsiveness to homeostatic signals. Qa2, the expression of which indicates the phenotypic maturation of SPs and RTEs, was found to be upregulated in CD4(+) pre-RTEs in thymic perivascular space. Migratory dendritic cells that surround this region contribute to Qa2 expression in pre-RTEs. The dendritic cell-driven Qa2 induction of CD4(+) pre-RTEs is independent of MHC class II and Aire molecules.

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Dendritic cells promote the Qa2 upregulation of SP3 pre-RTEs.Purified SP3 thymocytes were cultured with IL-7 and FLDCs derived from C57BL/6 mice (A, B, E), and Aire-/- mice (C), and MHC class II-/- mice (D) for 4 days. The expression of Qa2 (B–D) and in some cases, Qa2 and CD69 (A) of live T cells were analyzed. (E) SP3 thymocytes upregulate their Qa2 expression in lymphoreplete mice. CFSE-labeled SP3 thymocytes were adoptively transferred into C57BL/6 mice. Qa2 expression was analyzed in CFSE+ T cells in the lymph nodes and spleen at 2 and 4 days post-transfer. The numbers show the percentage of Qa2+ cells. The experiments have been repeated for 3 times.
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pone-0056378-g007: Dendritic cells promote the Qa2 upregulation of SP3 pre-RTEs.Purified SP3 thymocytes were cultured with IL-7 and FLDCs derived from C57BL/6 mice (A, B, E), and Aire-/- mice (C), and MHC class II-/- mice (D) for 4 days. The expression of Qa2 (B–D) and in some cases, Qa2 and CD69 (A) of live T cells were analyzed. (E) SP3 thymocytes upregulate their Qa2 expression in lymphoreplete mice. CFSE-labeled SP3 thymocytes were adoptively transferred into C57BL/6 mice. Qa2 expression was analyzed in CFSE+ T cells in the lymph nodes and spleen at 2 and 4 days post-transfer. The numbers show the percentage of Qa2+ cells. The experiments have been repeated for 3 times.

Mentions: We have previously shown that thymic epithelial cells were required for Qa2 expression in the thymus that indicates the SP3-to-SP4 transition [5]. However, thymic epithelial cells purified from Aire-/- mice failed to induce Qa2 upregulation in wild type SP3 cells in vitro (Yu, S., Zhang, Y., manuscript in preparation). Thus, stromal cells other than epithelial cells may contribute to the induction of Qa2 expression in the thymic PVS in Aire-/- mice. Dendritic cell, including SIRPα- resident conventional DC (cDC), migratory SIRPα+ cDC, and migratory plasmacytoid DC (pDCs), is a type of thymic stromal cells that plays an important role in negative selection [32], [33], [34], [35], [36]. We thus examined whether DCs promote the phenotypic maturation of pre-RTEs. As only Flt3 ligand (Flt3L)-induced DCs (FLDCs) have been shown to enter the thymus via PVS region [37], [38], SP3 thymocytes (CD69-Qa2-) were purified from B6 mice and were cultured with FLDCs in vitro. To promote the survival of thymocytes, 1 ng/ml of IL-7 was added in the co-culture system. About 20% of SP3 cells upregulated their Qa2 when T cells were cultured with IL-7 alone, DCs alone, or cultured in the transwell with IL-7 and DCs (T cells in the upper well and DCs in the lower well) (Fig. 7A–B). However, more than 60% of T cells expressed Qa2 when they were cultured with IL-7 and DCs in the same well (Fig. 7A), suggesting that the cellular interaction between T and DCs was essential in this process. FLDCs deficient in Aire were further examined and similar levels of Qa2 expression were found in the culture with Aire-/- or wild type DCs (Fig. 7C).


Homeostatic properties and phenotypic maturation of murine CD4+ pre-thymic emigrants in the thymus.

Dong J, Chen Y, Xu X, Jin R, Teng F, Yan F, Tang H, Li P, Sun X, Li Y, Wu H, Zhang Y, Ge Q - PLoS ONE (2013)

Dendritic cells promote the Qa2 upregulation of SP3 pre-RTEs.Purified SP3 thymocytes were cultured with IL-7 and FLDCs derived from C57BL/6 mice (A, B, E), and Aire-/- mice (C), and MHC class II-/- mice (D) for 4 days. The expression of Qa2 (B–D) and in some cases, Qa2 and CD69 (A) of live T cells were analyzed. (E) SP3 thymocytes upregulate their Qa2 expression in lymphoreplete mice. CFSE-labeled SP3 thymocytes were adoptively transferred into C57BL/6 mice. Qa2 expression was analyzed in CFSE+ T cells in the lymph nodes and spleen at 2 and 4 days post-transfer. The numbers show the percentage of Qa2+ cells. The experiments have been repeated for 3 times.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3569422&req=5

pone-0056378-g007: Dendritic cells promote the Qa2 upregulation of SP3 pre-RTEs.Purified SP3 thymocytes were cultured with IL-7 and FLDCs derived from C57BL/6 mice (A, B, E), and Aire-/- mice (C), and MHC class II-/- mice (D) for 4 days. The expression of Qa2 (B–D) and in some cases, Qa2 and CD69 (A) of live T cells were analyzed. (E) SP3 thymocytes upregulate their Qa2 expression in lymphoreplete mice. CFSE-labeled SP3 thymocytes were adoptively transferred into C57BL/6 mice. Qa2 expression was analyzed in CFSE+ T cells in the lymph nodes and spleen at 2 and 4 days post-transfer. The numbers show the percentage of Qa2+ cells. The experiments have been repeated for 3 times.
Mentions: We have previously shown that thymic epithelial cells were required for Qa2 expression in the thymus that indicates the SP3-to-SP4 transition [5]. However, thymic epithelial cells purified from Aire-/- mice failed to induce Qa2 upregulation in wild type SP3 cells in vitro (Yu, S., Zhang, Y., manuscript in preparation). Thus, stromal cells other than epithelial cells may contribute to the induction of Qa2 expression in the thymic PVS in Aire-/- mice. Dendritic cell, including SIRPα- resident conventional DC (cDC), migratory SIRPα+ cDC, and migratory plasmacytoid DC (pDCs), is a type of thymic stromal cells that plays an important role in negative selection [32], [33], [34], [35], [36]. We thus examined whether DCs promote the phenotypic maturation of pre-RTEs. As only Flt3 ligand (Flt3L)-induced DCs (FLDCs) have been shown to enter the thymus via PVS region [37], [38], SP3 thymocytes (CD69-Qa2-) were purified from B6 mice and were cultured with FLDCs in vitro. To promote the survival of thymocytes, 1 ng/ml of IL-7 was added in the co-culture system. About 20% of SP3 cells upregulated their Qa2 when T cells were cultured with IL-7 alone, DCs alone, or cultured in the transwell with IL-7 and DCs (T cells in the upper well and DCs in the lower well) (Fig. 7A–B). However, more than 60% of T cells expressed Qa2 when they were cultured with IL-7 and DCs in the same well (Fig. 7A), suggesting that the cellular interaction between T and DCs was essential in this process. FLDCs deficient in Aire were further examined and similar levels of Qa2 expression were found in the culture with Aire-/- or wild type DCs (Fig. 7C).

Bottom Line: Qa2, the expression of which indicates the phenotypic maturation of SPs and RTEs, was found to be upregulated in CD4(+) pre-RTEs in thymic perivascular space.Migratory dendritic cells that surround this region contribute to Qa2 expression in pre-RTEs.The dendritic cell-driven Qa2 induction of CD4(+) pre-RTEs is independent of MHC class II and Aire molecules.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Medical Immunology, Ministry of Health, Department of Immunology, Peking University Health Science Center, Beijing, China.

ABSTRACT
After a tightly regulated developmental program in the thymus, "mature" single positive (SP) thymocytes leave the thymus and enter the periphery. These newly arrived recent thymic emigrants (RTEs) are phenotypically and functionally immature, and will complete a dynamic maturation in the peripheral lymphoid organs before being licensed to be resident naïve T cells. To study the early events occurring in the RTE maturation process, we identified the phenotype of CD4(+) pre-RTEs, a population of CD4(+) SP thymocytes that have acquired the thymus egress capability. Compared to peripheral naïve T cells, CD4(+) pre-RTEs displayed superior survival capability in lymphoreplete mice and faster proliferation under lymphopenic condition. The differences in Bcl2/Bim expression and/or heightened IL-7 signaling pathway may account for the pre-RTEs' better responsiveness to homeostatic signals. Qa2, the expression of which indicates the phenotypic maturation of SPs and RTEs, was found to be upregulated in CD4(+) pre-RTEs in thymic perivascular space. Migratory dendritic cells that surround this region contribute to Qa2 expression in pre-RTEs. The dendritic cell-driven Qa2 induction of CD4(+) pre-RTEs is independent of MHC class II and Aire molecules.

Show MeSH
Related in: MedlinePlus