Exp Mol Med.  2009 Dec;41(12):896-911. 10.3858/emm.2009.41.12.095.

Expression of 4-1BB and 4-1BBL in thymocytes during thymus regeneration

• Kim YM
• Kim HK
• Kim HJ
• Lee HW
• Ju SA
• Choi BK
• Kwon BS
• Kim BS
• Kim JB
• Lim YT
• Yoon S

• KMID: 1099866
• DOI: http://doi.org/10.3858/emm.2009.41.12.095

Abstract

4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is a major costimulatory receptor that is rapidly expressed on the surface of CD4+ and CD8+ T cells after antigen- or mitogen-induced activation. The interaction of 4-1BB with 4-1BBL regulates immunity and promotes the survival and expansion of activated T cells. In this study, the expression of 4-1BB and 4-1BBL was examined during regeneration of the murine thymus following acute cyclophosphamide-induced involution. Four-color flow cytometry showed that 4-1BB and 4-1BBL were present in the normal thymus and were preferentially expressed in the regenerating thymus, mainly in CD4+CD8+ double-positive (DP) thymocytes. Furthermore, the CD4loCD8lo, CD4+CD8lo and CD4loCD8+ thymocyte subsets, representing stages of thymocyte differentiation intermediate between DP and single-positive (SP) thymocytes, also expressed 4-1BB and 4-1BBL during thymus regeneration but to a lesser degree. Interestingly, the 4-1BB and 4-1BBL positive cells among the CD4+CD8+ DP thymocytes present during thymus regeneration were TCR(hi) and CD69+ unlike the corresponding controls. Moreover, the 4-1BB and 4-1BBL positive cells among the intermediate subsets present during thymus regeneration also exhibited TCRhi/int and CD69+/int phenotypes, indicating that 4-1BB and 4-1BBL are predominantly expressed by the positively selected population of the CD4+CD8+ DP and the intermediate thymocytes during thymus regeneration. RT-PCR and Western blot analyses confirmed the presence and elevated levels of 4-1BB and 4-1BBL mRNA and protein in thymocytes during thymus regeneration. We also found that the interaction of 4-1BB with 4-1BBL promoted thymocyte adhesion to thymic epithelial cells. Our results suggest that 4-1BB and 4-1BBL participate in T lymphopoiesis associated with positive selection during recovery from acute thymic involution.

Keyword

4-1BB ligand; antigens, CD137; cell differentiation; thymus gland; T-lymphocytes

MeSH Terms

4-1BB Ligand/genetics/*metabolism
Animals
Antigens, CD137/genetics/*metabolism
CD4-Positive T-Lymphocytes/cytology/metabolism
CD8-Positive T-Lymphocytes/cytology/metabolism
Cell Adhesion
Cell Differentiation
Cell Line
Cells, Cultured
Cyclophosphamide/pharmacology
Epithelial Cells/cytology
Gene Expression Regulation
Immunosuppressive Agents/pharmacology
Male
Mice
Mice, Inbred C57BL
RNA, Messenger/genetics
*Regeneration
T-Lymphocytes/*cytology/metabolism
Thymus Gland/*cytology/drug effects/*physiology