Adoptive transfer of T-cell precursors enhances T-cell reconstitution after allogeneic hematopoietic stem cell transplantation.

Immunoincompetence after allogeneic hematopoietic stem cell transplantation (HSCT) affects in particular the T-cell lineage and is associated with an increased risk for infections, graft failure and malignant relapse. To generate large numbers of T-cell precursors for adoptive therapy, we cultured mouse hematopoietic stem cells (HSCs) in vitro on OP9 mouse stromal cells expressing the Notch-1 ligand Delta-like-1 (OP9-DL1). We infused these cells, together with T-cell-depleted mouse bone marrow or purified HSCs, into lethally irradiated allogeneic recipients and determined their effect on T-cell reconstitution after transplantation. Recipients of OP9-DL1-derived T-cell precursors showed increased thymic cellularity and substantially improved donor T-cell chimerism (versus recipients of bone marrow or HSCs only). OP9-DL1-derived T-cell precursors gave rise to host-tolerant CD4+ and CD8+ populations with normal T-cell antigen receptor repertoires, cytokine secretion and proliferative responses to antigen. Administration of OP9-DL1-derived T-cell precursors increased resistance to infection with Listeria monocytogenes and mediated significant graft-versus-tumor (GVT) activity but not graft-versus-host disease (GVHD). We conclude that the adoptive transfer of OP9-DL1-derived T-cell precursors markedly enhances T-cell reconstitution after transplantation, resulting in GVT activity without GVHD.

Pathogen-specific CD8 T cell responses are directly inhibited by IL-10.

Regulation of CD8 T cell expansion and contraction is essential for successful immune defense against intracellular pathogens. IL-10 is a regulatory cytokine that can restrict T cell responses by inhibiting APC functions. IL-10, however, can also have direct effects on T cells. Although blockade or genetic deletion of IL-10 enhances T cell-mediated resistance to infections, the extent to which IL-10 limits in vivo APC function or T cell activation/proliferation remains unknown. Herein, we demonstrate that primary and memory CD8 T cell responses following Listeria monocytogenes infection are enhanced by the absence of IL-10. Surface expression of the IL-10R is transiently up-regulated on CD8 T cells following activation, suggesting that activated T cells can respond to IL-10 directly. Consistent with this notion, CD8 T cells lacking IL-10R2 underwent greater expansion than wild-type T cells upon L. monocytogenes infection. The absence of IL-10R2 on APCs, in contrast, did not enhance T cell responses following infection. Our studies demonstrate that IL-10 produced during bacterial infection directly limits expansion of pathogen-specific CD8 T cells and reveal an extrinsic regulatory mechanism that modulates the magnitude of memory T cell responses.

Cross-recognition of N-formylmethionine peptides is a general characteristic of H2-M3-restricted CD8+ T cells.

H2-M3-restricted CD8+ T cells can exhibit cross-reactivity to different bacterially derived N-formylmethionine peptides. The extent of this promiscuity is unclear. We deleted the nonredundant fMIVTLF epitope and found that Listeria monocytogenes still primed fMIVTLF-specific T cells. Thus, cross-reactivity appears to be a more general characteristic of H2-M3-restricted T cells.