BDCA-1+, BDCA-2+ and BDCA-3+ dendritic cells in early human pregnancy decidua

Abstract

Dendritic cells (DCs) can acquire unique features or phenotypes in different tissue microenvironments and decide whether immunity or tolerance develops. DCs observed within the decidua have been implicated in pregnancy maintenance. However, the precise distribution of decidual DC subsets and their phenotypic characteristics are largely unknown. Using flow cytometry, we identified three DC subsets in normal human first-trimester decidua: BDCA-1+ CD19- CD14(-) myeloid DC type 1 (MDC1), BDCA-3+ CD14- myeloid DC type 2 (MDC2) and BDCA-2+ CD123+ plasmacytoid DC (PDC). The percentage of MDC1 to mononuclear cells in the decidua was similar to that in the peripheral blood controls. The percentage of MDC2 in the decidua was significantly higher than that in the peripheral blood controls, whereas the percentage of PDC was significantly lower. Both MDC1 and MDC2 subsets expressed human leucocyte antigen D-related, CD86 and CD80 at low levels, suggesting a characteristic of immature myeloid DCs. Immunoglobulin-like transcript 3, suggested to be involved in immune tolerance induction, was also expressed on decidual MDC1 and MDC2 subsets. In addition, as gestational age increased from 6 to 9 weeks, the numbers of MDC1 decreased but MDC2 increased significantly. This is the first study to demonstrate the presence of three previously unidentified BDCA-1+, BDCA-3+ and BDCA-2+ DC subsets in human decidua, these decidual DCs might play important role in the maintenance of pregnancy.

Fig. 1

Gating strategy used to identify BDCA-1⁺, BDCA-3⁺ and BDCA-2⁺ dendritic cell (DC) subsets in decidua by flow cytometry. (a) The R1 gate was drawn on the basis of forward and side scatter (FSC and SSC) to exclude cell debris and dead cells. (b) The events falling in the R1 gate were analysed in terms of staining for BDCA-1, CD14 and CD19, and BDCA-1⁺CD14^-CD19^- cells were characterized as myeloid DC type 1 (MDC1). (c) The R1-gated events were then analysed in terms of staining for BDCA-3 and CD14, and BDCA-3⁺ CD14^– cells were characterized as myeloid DC type 2 (MDC2). (d) The R1-gated events were then analysed in terms of staining for BDCA-2 and CD123, and BDCA-2⁺ CD123⁺ cells were characterized as plasmacytoid DC (PDC). Representative stainings from one sample are shown.

Fig. 2

BDCA⁺ dendritic cell (DC) subsets percentages in decidua (n = 44) and peripheral blood (PB) controls (n = 26). Percentages of (a) BDCA-1⁺, (b) BDCA-3⁺ and (c) BDCA-2⁺ DC subsets to decidual mononuclear cells in decidua and the corresponding DC subpopulations to peripheral blood mononuclear cells in peripheral blood controls were analysed by flow cytometry. Results are presented in box-and-whisker plots, which demonstrate the median (horizontal lines within the boxes), the quartiles (boxes), the smallest and greatest values (whiskers outside boxes) and the outliers (small circles) in the distribution. *P < 0·05.

Fig. 3

Expression of humal leucocyte antigen D-related (HLA-DR), CD86 and CD80 on BDCA-1⁺ dendritic cell (DC) and BDCA-3⁺ DC subsets. (a) Expression of these antigens on BDCA-1⁺ DC and BDCA-3⁺ DC subsets from decidua as well as from peripheral blood (PB) controls were analysed. Representative stainings from one sample are shown. (b) The geometric mean fluorescence intensity of these antigens on BDCA-1⁺ DC (n = 11) and BDCA-3⁺ DC (n = 11) subsets from decidua were compared with PB controls. Dots linked with a line represent samples from the same individual. (c) Expression of immunoglobulin-like transcript 3 on BDCA-1⁺ DC and BDCA-3⁺ DC subsets from decidua were analysed. Representative stainings from one sample are shown.The bold lines show cells staining with the indicated markers, and the faint lines show cells staining with isotype matched controls. *P < 0·05.

Fig. 4

Number changes of decidual BDCA-1⁺, BDCA-3⁺ and BDCA-2⁺ dendritic cell (DC) subsets with gestational age. As gestational age increased from 6 to 9 weeks, the numbers of (a) BDCA-1⁺ DC subsets decreased, (b) but BDCA-3⁺ DC subsets increased significantly. There were no significant differences of BDCA-2⁺ DC subsets with increasing gestational age (for each weeks of gestation n = 11). Results are presented in box-and-whisker plots, which demonstrate the median (horizontal lines within the boxes), the quartiles (boxes), the smallest and greatest values (whiskers outside boxes) and the outliers (small circles) in the distribution. *P < 0·05.