RAP1A and immunoglobulin G4-related sclerosing disease: Genes (or proteins) related to several signaling pathways were also detected in IgG4-RD samples (tissue or PBMC), including MAPK signaling pathway, PI3K-Akt signaling pathway, Ras signaling pathway, TGF-β signaling pathway, NF-κB signaling pathway and Rap1 signaling pathway (Figures 2A, 3, Table 4, Table S7).