RT Journal Article SR Electronic T1 Localisation of lysozyme mRNA in rheumatoid synovial membrane by in situ hybridisation. JF Annals of the Rheumatic Diseases JO Ann Rheum Dis FD BMJ Publishing Group Ltd and European League Against Rheumatism SP 912 OP 917 DO 10.1136/ard.48.11.912 VO 48 IS 11 A1 Konttinen, Y T A1 Bergroth, V A1 Kulomaa, M A1 Nordström, D A1 Segerberg-Konttinen, M A1 Keinänen, R A1 Kemppinen, P A1 Hukkanen, M A1 Grönblad, M YR 1989 UL http://ard.bmj.com/content/48/11/912.abstract AB Type A synovial lining cells have been shown to contain lysozyme in their lysosomes. This might be phagocytosed because synovial fluid contains lysozyme originating from tissue macrophages and articular cartilage but in arthritides, in particular, from neutrophils. In situ hybridisation with 35S labelled cDNA was used to detect mRNA for lysozyme over synovial lining in patients with rheumatoid arthritis. No hybridisation was found with lactoferrin cDNA, which was used as a negative control. Computer search against the EMBL gene bank (release 14) did not show any significant cross hybridisation to a known sequence. In cytological specimens 35S-cDNA:mRNA hybrids were observed in positive but not in negative control cells. The presence of lysozyme and its mRNA suggests that type A synovial lining cells are of mononuclear phagocyte lineage.