Relationship between the functional activity of <i>in vitro</i> generated monocyte-derived dendritic cells and the presence of CD16 ⁺ cells among peripheral blood monocytes

Abstract

Peripheral blood monocytes are heterogeneous CD14+ cell population, some of which also express CD16 molecule. Differences in phenotype between monocyte subpopulations can affect their functional activity, as well as the ability to further differentiate into dendritic cells (DCs). DCs are professional antigen-presenting cells which induce the immune response or, conversely, maintain the immunological tolerance. The aim of the present study was to analyze the relationship between monocyte subpopulations and the functional activity of monocyte-derived DCs, as well as DC sensitivity to the tolerogenic effect of dexamethasone. DCs were generated by cultivating enriched fractions of CD14+ monocytes with or without CD16+ cell depletion (CD16-Mo-DCs or CD16+Mo-DCs, respectively) in the presence of IFNα and GM-CSF. Monocyte subpopulations were obtained by immunomagnetic negative selection. CD16+Mo-DCs were characterized by lower ability to take up FITC-dextran and higher allostimulatory activity compared to CD16-Mo-DCs. In addition, CD16+Mo-DCs showed higher apoptosis-inducing activity against autologous CD4+T lymphocytes and allogeneic CD8+T lymphocytes, but were similar to CD16-Mo-DCs in their ability to induce apoptosis in allogeneic CD4+T lymphocytes. TNFa production level, similar for both types of DCs, was negatively correlated with CD16-Mo-DC allostimulatory activity and directly correlated with apoptosis-inducing activity of CD16+Mo-DCs towards allogeneic CD4+T cells. CD16-Mo-DCs and CD16+Mo-DCs were similar by their IL-10 production, which was inversely related to allostimulatory activity of both types of DCs. Dexamethasone increased endocytic activity, decreased the ability to stimulate autologous and allogeneic T cells, inhibited TNFα production of CD16-Mo-DCs and CD16+Mo-DCs. However, CD16+Mo-DCs demonstrated a more pronounced increase in endocytic activity and more dramatic decrease in their ability to stimulate the proliferation of CD4+T cells in auto-MLR. Also, addition of dexamethasone into CD16+Mo-DCs cultures led to the increase in DC pro-apoptogenic activity against autologous CD8+T lymphocytes. Thus, the presence of CD16+ cells among monocyte population affects the properties of IFNα-induced monocyte-derived DCs and DC sensitivity to the immunomodulatory effects of dexamethasone.

Keywords

• dendritic cells
• classical monocytes
• non-classical monocytes
• interferon-alpha
• dexamethasone