Mo A. Dao

IL-7 Enhances the Responsiveness of Human T Cells That Develop in the Bone Marrow of Athymic Mice

The beige/nude/xid/human (bnx/hu) model of human hematopoiesis provides a unique opportunity to study extrathymic human T lymphocyte development in an in vivo system. Purified human hematopoietic stem cells develop into mature T lymphocytes and immature progenitors in the bone marrow of athymic bnx mice. The human T cells are all TCRαβ+ and display a restricted TCRVβ repertoire. In the current studies, we examined the effects of systemic human IL-7 (huIL-7) administration on the phenotype and the activation status of the bnx/hu T cells. In the majority of the mice that did not have huIL-7 administration, a higher frequency of human CD3+/CD8+ than CD3+/CD4+ T cells developed in the bone marrow. This phenomenon is also frequently observed in human bone marrow transplant recipients. Extremely low levels of IL-2 were expressed by human CD3+ cells isolated from these mice, in response to PMA plus ionomycin and to CD3 and CD28 cross-linking. IL-4 was not expressed by cells exposed to either stimulus, demonstrating a profound inability of the bnx/hu T cells to produce this cytokine. Systemic production of huIL-7 from engineered stromal cells transplanted into the mice increased the human CD4 to CD8 ratios, and increased the ratio of memory to naive CD4+ and CD8+ T cells. The human CD3+ cells recovered from mice that had systemic huIL-7 and equivalent numbers of CD3+/CD4+ and CD3+/CD8+ cells in the marrow were still unable to produce IL-4 in response to any condition tested, but were capable of normal levels of IL-2 production following stimulation.

Immunosuppressive Activity of Adult Marrow Mesenchymal Stromal Cells on Innate Immune Cells in the Central Nervous System

Adult marrow derived mesenchymal stromal cells are currently in clinical trials for various neurodegenerative diseases. Through secretion of soluble and insoluble trophic factors, mesenchymal stromal cells promote the endogenous stem and progenitor cells to repair damaged tissues. At the same time, mesenchymal stromal cells control the inflammation that often co-exists with tissue injury. In the central nervous system, the major immune components are the innate immune cells. In the current review, we will highlight and discuss the in vitro and in vivo studies in which MSCs have been shown to regulate innate immune cells in the central nervous system.

Retroviral-mediated transduction and clonal integration analysis of human hematopoietic stem and progenitor cells.

This chapter provides information on the methods used to introduce genes into human hematopoietic stem and progenitor cells, using Moloney Murine Leukemia (MoMuLV)-based retroviral vectors. MoMuLV-based vectors have the ability to efficiently transfer genes into mammalian cells, leading to permanent integration of a single copy of the gene of interest into the cellular chromosomes. The technique of single-colony inverse [polymerase chain reaction (PCR) can be used to track individual descendants of MoMuLV-vector-transduced hematopoietic stem cells (HSC), by capitalizing upon the unique restriction patterns generated by the random integration events (1-2). Methods to adapt the inverse PCR technology to the use of other vector systems, such as lentiviral or adeno-associated virus (AAV) vectors, are currently under development. These techniques will be necessary to determine the efficacy of the newer vector systems in transducing individual human HSC that have the capacity to generate both lymphoid and myeloid progeny, as has been demonstrated in rare occurrences using MoMuLV-based vectors (2).