Vasoactive intestinal peptide receptors (VPAC) 1 and VPAC2 are expressed on SS-associated macrophages, with higher expression observed in M1 compared to M2 macrophages [59]. A study has shown that vasoactive intestinal peptide (VIP), an endogenous ligand for VPAC1 and VPAC2, can alleviate SS-related symptoms by inhibiting the PI3K/AKT pathway to restore the balance between Treg and Th17 cells [60]. Therefore, VIP has been reported as a candidate drug with anti-inflammatory and immunomodulatory properties for the treatment of SS. This evidence concerns the gene VIPR1 and synovial sarcoma.