S1PR1 and systemic lupus erythematosus: Next, we compared expression of S1PR1 transcripts in synovial ECs from patients with RA with that in healthy controls using single-cell RNA-Seq from 3 data sets: Accelerating Medicines Partnership Rheumatoid Arthritis/Systemic Lupus Erythematosus (AMP RA/SLE) network (57), the Roche network for RA (58), and Faust et al. (59) for normal synovium.