Fig. 1. Human blood basophils from SLE patients overexpress PD-L1.

a Flow cytometry gating strategy used to identify human circulating T follicular helper T cells (cTFH) defined as CD3⁺ CD8α^– CD4⁺ CXCR5⁺ ICOS⁺ PD-1⁺. Among cTFH cells, cTFH1 cells were defined as CXCR3⁺CCR6^–, cTFH2 as CXCR3^– CCR6^–, and cTFH17 as CXCR3^– CCR6⁺. b Proportions (%) among CD4⁺ T cells of cTFH as defined in (a) in blood from healthy controls (CT) and inactive (inact.), mild, or active SLE patients (n = 16/11/12/21) as determined by flow cytometry. Proportions (%) among CD4⁺ T cells of cTFH2 (c), cTFH1 (d) and cTFH17 (e) as defined in (a) in blood from healthy controls and inactive, mild, or active SLE patients (n = 16/10/12/20) as determined by flow cytometry. f Correlation (and linear regression with 95% confidence intervals) between Log (cTFH2 cell numbers per mL of blood) and SLEDAI (Spearman r = 0.3682, p = 0.02, n = 37). g Left, Histogram plot representing the CD203c expression levels on blood basophils from a healthy control (CT, black), a patient with active SLE (red), and isotype control staining (gray filled). Right, CD203c expression levels on blood basophils from CT and inact, mild or active SLE patients (n = 43/61/46/98) as determined by flow cytometry. h Left, Representative histogram plot of PD-L1 expression levels on blood basophils as in (g). Right, PD-L1 expression levels on blood basophils from CT and inact, mild or active SLE patients (n = 39/60/45/96) as determined by flow cytometry. (b–e, g, h) Data are presented as violin plots with median (solid line) and quartiles (dotted lines). Statistical analyses were Kruskal–Wallis tests followed by Dunn’s multiple comparisons tests and p values are shown above each bracket. NS not significant. A.U. arbitrary units. Source data are provided in the Source Data file.