Cells with dendritic cell morphology and immunophenotype, binuclear morphology, and immunosuppressive function in dendritic cell cultures

Culturing of human peripheral blood CD14 positive monocytes is a method for generation of dendritic cells (DCs) for experimental purposes or for use in clinical grade vaccines. When culturing human DCs in this manner for clinical vaccine production, we noticed that 5–10% of cells within the bulk culture were binuclear or multiple nuclear, but had typical dendritic cell morphology and immunophenotype. We refer to the cells as binuclear cells in dendritic cell cultures (BNiDCs). By using single cell PCR analysis of mitochondrial DNA polymorphisms we demonstrated that approximately 20–25% of cells in DC culture undergo a fusion event. Flow sorted BNiDC express low HLA-DR and IL-12p70, but high levels of IL-10. In mixed lymphocyte reactions, purified BNiDC suppressed lymphocyte proliferation. Blockade of dendritic cell-specific transmembrane protein (DC-STAMP) decreased the number of binuclear cells in DC cultures. BNiDC represent a potentially tolerogenic population within DC preparations for clinical use.

► We describe the existence of cells with binuclear and multinuclear appearance in human dendritic cell cultures.
► Binuclear and multinuclear cells contain diploid or more DNA content.
► Binuclear cells can carry cytoplasm from two separate donors in allogeneic culture.
► Binuclear cells can suppress activity of mononuclear dendritic cells within the same culture.