P2RX4 and synovial sarcoma: In the salivary glands, several purinergic receptors are expressed and upregulated under pathological conditions, including SS (Schrader et al., 2005; Baldini et al., 2013), where their activation mediates inflammatory and immune responses (Baker et al., 2008; Khalafalla M.G. et al., 2017), as well as cell repair mechanisms (El-Sayed et al., 2014).