Reduced blood BDCA-2+ (lymphoid) and CD11c+ (myeloid) dendritic cells in systemic lupus erythematosus

Abstract

Type 1 IFN is thought to be implicated in the autoimmune process of SLE. Plasmacytoid dendric cells (DC), which are natural IFN-alpha producing cells, play a pivotal epipathogenic role in SLE. The present study was undertaken to investigate the phenotypic characteristics of peripheral blood DC in SLE patients in comparison with those of healthy controls. Samples from 20 SLE patients and 18 healthy controls were studied. Three-colour flow cytometry was performed to identify myeloid DC, as CD11c(+) lineage marker(-), and HLA-DR(+) cells and plasmacytoid DC, as BDCA-2(+) linage marker(-), and HLA-DR(+) cells. We used the whole blood 'lyse/no-wash' procedure, which allows precise counting of peripheral blood DC. BDCA-2(+) plasmacytoid DC and CD11c(+) myeloid DC were reduced in SLE patients compared with controls. Similarly, BDCA-3(+) DC were reduced in SLE patients. These results indicated that SLE patients had a reduced number of both BDCA-2(+) plasmacytoid DC and CD11c(+) myeloid DC. These alternations of the DC subset may drive the autoimmune response in SLE.

Fig. 1

Gating strategy used to define BDCA-2⁺ and CD11c⁺ DCs by flowcytometry. Peripheral blood mononuclear cells were selected in the R1 gate excluding debris and polynuclear cells (a). Lineage-negative and HLA-DR-positive cells were selected in the R2 gate (b). In this combined R1 and R2 gate, CD11c⁺, HLA-DR⁺ (c)(R3) or BDCA-2⁺, HLA-DR⁺ (d)(R3) events were quantified.

Fig. 2

(a) Blood BDCA-2⁺ DC percentage in SLE patients and healthy controls. Percentages of BDCA-2⁺ DC were analysed by flow cytometry as shown in Fig. 1. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test. (b) Blood BDCA-2⁺ DC absolute numbers in SLE patients and healthy controls. Absolute numbers of BDCA-2⁺ DC were calculated using the percentage of BDCA-2⁺ DC and the mononuclear cell count determined by the automated haematology blood analysis. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test.

Fig. 3

(a) Blood CD11c⁺ DC percentage in SLE patients and healthy controls. Percentages of CD11c⁺ DC were analysed by flow cytometry as shown in Fig. 1. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test. (b) Blood CD11c⁺ DC absolute numbers in SLE patients and healthy controls. Absolute numbers of CD11c⁺ DC were calculated using the percentage of CD11c⁺ DC and the mononuclear cell count determined by the automated haematology blood analysis. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test.

Fig. 4

(a) Blood BDCA-3⁺ DC percentage in SLE patients and healthy controls. Percentages of BDCA-3⁺ DC were analysed by flow cytometry as shown in Fig. 1. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test. (b) Blood BDCA-3⁺ DC absolute numbers in SLE patients and healthy controls. Absolute numbers of BDCA-3⁺ DC were calculated using the percentage of BDCA-3⁺ DC and the mononuclear cell count determined by the automated haematology blood analysis. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test.

Fig. 5

Blood DC percentages in RA patients and healthy controls.Percentages of (a) BDCA-2⁺, (b) CD11c⁺ and (c) BDCA-3⁺ DC were analysed by flow cytometry as shown in Fig. 1. Boxes show the 25th and 75th percentiles. Horizontal lines within the boxes show the median. Bars above and below the boxes show the 10th and 90th percentiles. Significance levels for differences between groups were analysed by the Mann–Whitney U-test.

Fig. 6

(a) The CD11c⁺: BDCA-2⁺ DC ratio in SLE patients (n = 20) and healthy controls (n = 18). (b) The BDCA-3⁺: BDCA-2⁺ DC ratio in SLE patients (n = 20) and healthy controls (n = 18).

Fig. 7

(a) Correlation between BDCA-2⁺ DC and peripheral blood lymphocyte counts. The percentages of BDCA-2⁺ DC were determined by flow cytometry. Peripheral blood lymphocyte counts were determined by the automated haematology blood analysis. (b) Correlation between BDCA-2⁺ plus CD11c⁺ DC and peripheral blood lymphocyte counts. (c) Correlation between CD11c⁺ DC and peripheral blood lymphocyte counts. (d) Correlation between BDCA-3⁺ DC and peripheral blood lymphocyte counts.