In addition, we identified a total of 15 upregulated signaling ligand-receptor pairs (including CCL3-CCR1, CCL3L1-CCR1, IFNG-IFNGR1:IFNGR2, TNF-TNFRSF1B, etc.)(Supplementary 7) and 68 downregulated signaling ligand-receptor pairs (including CCL5-CCR1, MIF-CD74:CXCR4, MIF-CD74:CD44, IL16-CD4, etc.)(Supplementary 8) based on differential gene expression analysis by comparing ligand-receptor pairs and the communication probabilities between RA and Ctrl samples for each cell group pair. The gene discussed is CD44; the disease is rheumatoid arthritis.