Dendritic cell differentiation and proliferation: enhancement by tumor necrosis factor-alpha

Dendritic cells (DCs) are a diverse group of hematopoietic-derived cells that play a prominent role in initiating the body's immune response. Tumor necrosis factor-alpha (TNFalpha) aids CD34+ hematopoietic stem cells in the development of DCs. In this study, we aimed to further define the relationship between TNFalpha and DC maturation. CD34+ stem cells were isolated from umbilical cord blood and cultured using granulocyte-macrophage colony stimulating factor, stem cell factor, and varying concentrations of TNFalpha. An anti-TNF receptor 1 (anti-TNFR1) antibody was used to show the specificity of TNFalpha. Flow cytometry and light microscopy analyses were performed at days 0, 7, and 14 of culture, revealing mature DCs at all concentrations of TNFalpha by day 14, excluding those with anti-TNFR1 bound to the cell's TNF receptor 1. DCs possessed a characteristic veiled appearance and were consistent with a DC panel of surface markers. TNFalpha was essential to the development of DCs, as those with bound anti-TNFR1 were virtually unable to develop into DCs. Increasing TNFalpha enhanced the survival of culturing stem cells and resulted in a parallel increase in day 14 DCs. Although increases in TNFalpha produced more DCs, these cells were not as phenotypically mature, expressing less CD80 than those receiving only a single initial dosage of TNFalpha. These studies support the prevalence of large numbers of DCs under inflammatory conditions, such as the rheumatoid joint, where local concentrations of TNFalpha are high.