S100A9 and rheumatoid arthritis: As shown by IPA network, changes of S100A9 protein expression levels are known in literature to be associated with autoimmune systemic inflammatory diseases such as rheumatoid arthritis [20] and diffuse systemic sclerosis [21], [22] while an increase of IGKC and IGHA1 proteins was found in saliva belonging to non-Hodgkin's lymphoma patient in comparison with primary Sjögren syndrome [23], directly correlated to the lymphoproliferative process.