Abstract
Dendritic cell (DC)-based adoptive tumor immunotherapy approaches have shown promising results, but the incidence of tumor regression is low and there is an evident call for identifying culture conditions that produce DCs with a more potent Th1 potential. Routinely, DCs are differentiated in CO(2) incubators under atmospheric oxygen conditions (21% O(2)), which differ from physiological oxygen levels of only 3-5% in tissue, where most DCs reside. We investigated whether differentiation and maturation of DCs under physiological oxygen levels could produce more potent T-cell stimulatory DCs for use in adoptive immunotherapy. We found that immature DCs differentiated under physiological oxygen levels showed a small but significant reduction in their endocytic capacity. The different oxygen levels did not influence their stimuli-induced upregulation of cluster of differentiation 54 (CD54), CD40, CD83, CD86, C-C chemokine receptor type 7 (CCR7), C-X-C chemokine receptor type 4 (CXCR4) and human leukocyte antigen (HLA)-DR or the secretion of interleukin (IL)-6, tumor necrosis factor (TNF)-α and IL-10 in response to lipopolysaccharide (LPS) or a cytokine cocktail. However, DCs differentiated under physiological oxygen level secreted higher levels of IL-12(p70) after exposure to LPS or CD40 ligand. Immature DCs differentiated at physiological oxygen levels caused increased T-cell proliferation, but no differences were observed for mature DCs with regard to T-cell activation. In conclusion, we show that although DCs generated under atmospheric or physiological oxygen conditions are mostly similar in function and phenotype, DCs differentiated under physiological oxygen secrete larger amounts of IL-12(p70). This result could have implications for the use of ex vivo-generated DCs for clinical studies, since DCs differentiated at physiological oxygen could induce increased Th1 responses in vivo.
Highlights
Dendritic cells (DCs) are the most potent antigen-presenting cells [1,2] and are critical for the induction of immune responses to pathogens and cancer [1,3]
Cells were collected and T-cell proliferation was analyzed by flow cytometry gating on lymphocytes. (A) A representative result of three is shown. (B) The mean ± SD percentage of proliferating allogeneic T cells from three independent experiments using DCs and T cells from different donors. *Statistically significant difference, P < 0.05, Student t test. (C) Immature and mature DCs were generated and activated as above from human leukocyte antigen (HLA)-A*0201–positive donors, pulsed with 100 ng/mL HLA
Because DCs are the most potent initiators of antigen-specific T-cell responses, they have been applied toward immunotherapy of cancer and chronic infectious diseases
Summary
Dendritic cells (DCs) are the most potent antigen-presenting cells [1,2] and are critical for the induction of immune responses to pathogens and cancer [1,3]. Because of these properties, DCs are being widely used for vaccines and immunotherapeutic strategies [3,4,5,6,7,8,9,10]. One of the originally used maturation stimuli was monocyte-conditioned media [14], which was subsequently refined to a cocktail containing four components including prostaglandin E2 (PGE2), tumor necrosis factor (TNF)-α, IL-1β and IL-6 [8,25,26,27]
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