Transforming growth factor beta 1 (TGF beta 1) is shown here to be required for yolk sac haematopoiesis and endothelial differentiation. Mice with a targeted mutation in the TGF beta 1 gene were examined to determine the cause of prenatal lethality, which occurs in 50% of homozygous TGF beta 1 null (TGF beta 1-/-) conceptions. 50% of TGF beta 1-/- and 25% of TGF beta 1-+-) conceptions. 50% of TGF beta 1-/- and 25% of TGF beta 1+/- conceptuses were found to die at around 10.5 dpc. The primary defects were restricted to extraembryonic tissues, namely the yolk sac vasculature and haematopoietic system. The embryos per se showed developmental retardation, oedema and necrosis, which were probably secondary to the extraembryonic lesions. The defect in vasculogenesis appeared to affect endothelial differentiation, rather than the initial appearance and outgrowth of endothelial cells. Initial differentiation of yolk sac mesoderm to endothelial cells occurred, but defective differentiation resulted in inadequate capillary tube formation, and weak vessels with reduced cellular adhesiveness. Defective haematopoiesis resulted in a reduced erythroid cell number within the yolk sac. Defective yolk sac vasculogenesis and haematopoiesis were present either together, or in isolation of each other. The phenotypes are consistent with the observation of abundant TGF beta 1 gene expression in both endothelial and haematopoietic precursors. The data indicate that the primary effect of loss of TGF beta 1 function in vivo is not increased haematopoietic or endothelial cell proliferation, which might have been expected by deletion of a negative growth regulator, but defective haematopoiesis and endothelial differentiation.

Defective haematopoiesis and vasculogenesis in transforming growth factor-beta 1 knock out mice

Dendritic cells (DC) that are stimulated with inflammatory mediators can maturate and migrate from nonlymphoid tissues to lymphoid organs to initiate T cell-mediated immune responses. This migratory step is closely related to the maturation of the DC. In an attempt to identify chemokine receptors that might influence migration and are selectively expressed in mature DC, we have discovered that the chemokine receptor, EBI1/CCR7, is strikingly up-regulated upon maturation in three distinct culture systems: 1) mouse bone marrow-derived DC, 2) mouse epidermal Langerhans cells, and 3) human monocyte-derived DC. The EBI1/CCR7 expressed in mature DC is functional because ELC/MIP-3β, recently identified as a ligand of EBI1/CCR7, induces a rise in intracellular free calcium concentrations and directional migration of human monocyte-derived mature DC (HLA-DRhigh, CD1alow, CD14−, CD25+, CD83+, and CD86high) in a dose-dependent manner, but not of immature DC (HLA-DRlow, CD1ahigh, CD14−, CD25−, CD83−, and CD86−). In contrast, macrophage inflammatory protein-1α (MIP-1α), monocyte chemotactic protein-3 (MCP-3), and RANTES are active on immature DC but not on mature DC. Thus, it seems likely that MIP-1α, MCP-3, and RANTES can mediate the migration of immature DC located in peripheral sites, whereas ELC/MIP-3β can direct the migration of Ag-carrying DC from peripheral inflammatory sites, where DC are stimulated to up-regulate the expression of EBI1/CCR7, to lymphoid organs. It is postulated that different chemokines and chemokine receptors are involved in DC migration in vivo, depending on the maturation state of DC.

EBI1/CCR7 Is a New Member of Dendritic Cell Chemokine Receptor That Is Up-Regulated upon Maturation

Chemokine receptor expression by human intestinal epithelial cells.

Macrophage inflammatory protein 1 alpha (MIP-1 alpha) is a member of the C-C subfamily of chemokines, a large superfamily of low-molecular weight, inducible proteins that exhibit a variety of proinflammatory activities in vitro including leukocyte chemotaxis. MIP-1 alpha is a particularly interesting chemokine, because in addition to its proinflammatory activities, it inhibits the proliferation of hematopoietic stem cells in vitro and in vivo. Here, the biologic properties of MIP-1 alpha are reviewed in light of recent data on mice homozygous for a disruption of the MIP-1 alpha gene. The MIP-1 alpha null mice have no overt abnormalities of peripheral blood or bone marrow cells, indicating that MIP-1 alpha is not necessary for normal hematopoiesis. However, the MIP-1 alpha null mice have a mice have a reduced inflammatory reduced inflammatory response to influenza virus and are resistant to coxsackievirus-induced myocarditis. These data demonstrate that MIP-1 alpha is required for a normal inflammatory response to these viruses. Agent that inhibit the action of MIP-1 alpha may therefore prove useful for controlling inflammation in these and other settings.

The role of MIP-1 alpha in inflammation and hematopoiesis.

Megakaryocytic progenitors can be generated ex vivo and safely administered to autologous peripheral blood progenitor cell transplant recipients

Distinct and overlapping direct effects of macrophage inflammatory protein-1 alpha and transforming growth factor beta on hematopoietic progenitor/stem cell growth

Mariaestella Ortiz

Papers

Distinct and overlapping direct effects of macrophage inflammatory protein-1 alpha and transforming growth factor beta on hematopoietic progenitor/stem cell growth