Expression of c19orf10 in rheumatoid arthritis (RA) and osteoarthritis (OA) synovium. (a,d,f,h) Expression of c19orf10 in RA synovium. (b,c,e,g) Expression of c19orf10 in OA synovium. (a) Intense staining of the synovial lining layer and perivascular regions of RA (OCT section) tissue.(b) Intense staining of the synovial lining layer and perivascular regions of OA (paraffin section) tissue. (c) An area demonstrating a thin lining layer and perivascular region populated with c19orf10-positive cells. Note that the sublining stroma in this area is virtually devoid of c19orf10 staining. This pattern of staining is typical of that seen in both RA and OA sections. (d) In most lymphocytic aggregates, there was minimal staining of the lymphocytes although some mononuclear cells in the aggregates stained positively (arrow). (e) Intense staining of individual cells in the lining layer of a typical OA synovium. (f) An area of an OA synovium demonstrates a lining layer completely devoid of c19orf10 staining. (g) Intense staining of a hyperplastic RA synovial lining cell layer. This staining was typical of most areas of RA synovium where the lining was hyperplastic. (h) An area of an RA synovial lining layer that is not positive for c19orf10 staining. c19orf10, chromosome 19 open reading frame 10.