T-lymphocyte interaction with stromal, bone and hematopoietic cells in the bone marrow.
Mature T cells in the bone marrow (BM) are in constant exchange with the blood pool. Within the BM, T-cell recognition of antigen presented by dendritic cell (DC) can occur, nevertheless it is thought that BM T cells mostly receive non-antigenic signals by either stimulatory, for example, interleukin (IL)-7, IL-15, tumor necrosis factor family members, or inhibitory molecules, for example, transforming growth factor-beta. The net balance is in favor of T-cell proliferation. Indeed, the percentage of proliferating T cells is higher in the BM than in spleen and lymph nodes, both within CD4 and CD8 T cells. High numbers of memory T cells proliferate in the BM, as they preferentially home to the BM and have an increased turnover as compared with naive T cells. I propose here that the BM plays an essential role in maintaining normal peripheral T-lymphocyte numbers and antigen-specific memory for both CD4 and CD8 T cells. I also discuss BM T-cell contribution to the homeostasis of bone metabolism as well as of hematopoiesis. It emerges that BM T cells play unexpected roles in several diseases, for example AIDS and osteoporosis. A better knowledge on BM T cells has implications for currently used clinical interventions, for example, vaccination, BM transplantation, mesenchymal stem cell-based therapies.
Di Rosa
Francesca
F
Institute of Molecular Biology and Pathology, Consiglio Nazionale delle Ricerche, Rome, Italy. francesca.dirosa@uniroma1.it
D000818:Animals; D001853:Bone Marrow / Q000276:immunology*; D001842:Bone and Bones / Q000276:immunology* / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology*; D002465:Cell Movement / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D006410:Hematopoiesis / Q000276:immunology; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D006801:Humans; D017154:Stromal Cells / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology*
D016207:Cytokines