Additionally, we found that toothbrushes reduced salivary sTNF-R1 and sTNF-R2 in PBC patients, suggesting the involvement of reverse TNF signalling, where sTNFR1 and sTNFR2 bind to plasma membrane-bound TNF-α to activate reverse (outside-to-inside) TNF signalling in immune cells (48). The gene discussed is TNF; the disease is primary biliary cholangitis.