Fig 1: B1R is expressed in RA FLSs and ST.(A and B) IL-1β and TNF-α induced B1R mRNA and protein expression in RA FLSs in a time-dependent manner as determined by quantitative PCR and Western blotting. n = 3 RA FLSs used in each group. (C) B1R is highly expressed in RA in vivo. Immunofluorescence staining was performed targeting B1R (green), myeloid cell marker CD68 (red), fibroblast marker CD55 (red), EC marker vWF (red), and nuclear staining DAPI (blue). Representative pictures from 3 RA patients. Quantification was done by counting of B1R-positive cells in 5 fields per patient. Original magnification, ×200 and ×400. (D) Analysis of single-cell RNA-Seq data from Zhang et al. (71). showed that BDKRB1 is predominantly expressed on FLSs, while ANPEP and its sheddase MMP14 are expressed on FLSs and MNs. (E) All FLS (blue boxes) subsets coexpress ANPEP, MMP14, and BDKRB1, while the 2 MN clusters (red boxes) have high levels of ANPEP and MMP14 but low expression of BKDRB1. Results are shown as mean ± SD. *P < 0.05. Significance was determined by Kruskal-Wallis test or 1-way ANOVA (A).