The Role Of Notch Signaling On Human Monocytes Derived Dendritic Cell Differentiation And Function

Leukemia, a disease with high risk of relapse due to the residual leukemia cells after therapy, is critically hard to overcome in clinic. Studies on inhibition and removal of micro-residual focus by immunotherapy are becoming very important at the present stage.Dendritic cells (DC) are professional antigen presenting cells (APC) at present. Immature DCs mostly located in peripheral tissues are highly efficient at antigen (Ag) uptake by phagocytosis, receptor-mediated endocytosis, and macropinocytosis. After antigen uptake, DC will undergo maturation, become specialized in Ag presentation, and migrate into local lymph nodes to prime T-cell response or to maintain T-cell tolerance. These functional properties of DC are supported by morphological and molecular characteristics, including the expression of MHC class I and II, co-stimulatory and adhesion molecules, effectively boosting their ability to present processed peptides to antigen-specific T cells. At present, extensive attentions have been paid to the applications of DC in immunotherapy, especially in the studies on anti-tumor immunity through inducing cytotoxic T lymphocytes by tumor antigen loaded DC. Many in vivo and in vitro studies have been demonstrated the identified anti-tumor effect in leukemia treatment. Notch signaling is a highly revolutionarily conserved pathways involved in cell development, differentiation and cell fate decision. Activation of the Notch receptors is triggered by binding of its five ligands which are generally cell membrane associated. Studies have shown that immobilized human Delta1-ext-myc induced apoptosis in monocytes cultured with M-CSF but not GM-CSF. In the presence of GM-CSF, the protein could also promote differentiation of monocytes into immature DC but inhibit differentiation of monocytes into macrophages. We have previously demonstrated that up-regulation and deletion of Notch signaling could affect the development, differentiation and function of bone marrow derived DC in vitro in the presence of GM-SCF and IL-4. Up to now, effect of up-regulation or down-regulation of Notch signaling in DC on DC-dependent anti-tumor immunity has not been reported yet. In order to investigate whether the activation or inhibition of Notch signaling could affect the proliferation, differentiation and anti-tumor function of human monocytes derived DC.We investigated the effect of soluble human Delta-1 protein and GSI on development, differentiation and function of human monocyte derived DC from the following experiments:1. Explore the optimal concentrations of recombinant hDll1 and GSI in DC culture system.2. Detect the role of recombinant hDll1 and GSI in the proliferation and investigate the changes of CXCR4, HLA-DR and CD83 expression of human peripheral blood monocytes derived DC after loaded with LPS antigens.3. Study the T cell activation ability of DC cultured with hDll1 protein or GSI in the presence of GM-CSF and IL-4 in mixed lymphocyte reaction. We demonstrated that direct stimulation of Notch signaling in DC with soluble hDll1 protein can activate notch signaling pathways. DC maturation could be induced by low concentrations of hDll1 while inhibited by high concentrations of it. GSI could also inhibit DC maturation. The proliferation of DC could not be affected by up or down regulation of Notch signaling. Expression of HLA-DR, CXCR4 and CD83 were up-regulated after LPS antigen loading and the expression was higher on DC stimulated with hDll1 compared with GSI group. The CD8~+ T cell activation ability was stronger in DC stimulated with hDll1 than that or GSI. Therefore our findings might have important therapeutic implications in leukemia immunotherapy.