Increased Fc gamma receptor (FcγR)I, II and III expression in rheumatoid arthritis (RA) synovia. (a) Sequentially sectioned synovial biopsy from a healthy individual demonstrating FcγRII and III, but not FcγRI, positive cells. The same expression pattern was seen in all healthy volunteers studied (n = 10). (Original magnification ×250.) (b) Sequentially sectioned synovial tissue from a RA patient demonstrating FcγRI, II and III positive cells in the synovial lining and sub-lining layers and perivasculary. Note the dense staining of FcγRIII in the synovial lining layer. The FcγR stainings were representative of all other RA tissues stained (n = 26). IgG1 isotype control stainings were included for all the patient material used. (Original magnification ×125.) (c) The expression of FcγRs in healthy (n = 10), early (n = 11) and late RA (n = 15) synovial tissue was evaluated and compared. Note that FcγRI was not detected in healthy synovial tissue and that FcγRI, FcγRII and III were significantly more expressed in both early and late RA synovial tissue compared to healthy synovia (mean values of two independent observers, SEM and SK with standard error of the mean; **p < 0.01; ***p < 0.001). DAB, diaminobenzidine.