CD83 expression on dendritic cells and T cells: Correlation with effective immune responses

Human CD83 is a marker molecule for mature dendritic cells (DC) and is also expressed on activated B and T cells. Although CD83 has been implicated in immune responses, its function on DC and T cells remains unclear. In this study, we wanted to assess the role of CD83 expressed on DC and T cells in the immune response. Down-regulation of CD83 expression on human DC through RNA interference (RNAi) results in a less potent induction of allogeneic T cell proliferation, reduced IFN-gamma secretion by established T cells and decreased capacity in the priming of functional tumor antigen-specific CD8(+) T lymphocytes. In addition, CD83 mRNA-electroporated DC are stronger T cell stimulators. However, CD83 overexpression on Melan-A/MART-1-specific tumor-infiltrating lymphocytes (TIL) circumvents the need for CD83 expression on DC. Coculture of immature DC with TIL or K562 cells overexpressing CD83 results in the production of enhanced levels of pro-inflammatory cytokines, whereas this production is less pronounced or even absent in co-cultures with non-modified TIL or K562 cells. In conclusion, we demonstrate that CD83 expression on T cells and DC modulates the immune response by activating DC and by delivering costimulatory signals for the stimulation of naive and memory T cells, respectively.