Secretion of defensins from synovial tissue/cells and density of synovial neutrophils. (a) Levels of human neutrophil peptides 1-3 (HNP1-3) in superfusate of synovial tissue of two patients with rheumatoid arthritis (RA) and osteoarthritis (OA) (four replicates per patient). The dotted line indicates the detection limit. (b) Levels of human β-defensin-2 (HBD 2) in supernatant of synovial tissue of two patients with RA and OA (four replicates per patient). The dotted line indicates the detection limit. (c) Levels of defensins in supernatant of cultured mixed synovial cells over time. Compare the levels with the detection levels in panels (a) and (b). After 20 hours, HNP1-3 were in the detectable range, which was not the case for HBD-2. The data of four OA patients are given (two replicates of every patient), which was similar in RA patients (data not shown). (d) Density of synovial neutrophils in RA and OA synovial tissue. Every symbol represents the average density of neutrophils of one patient, as measured in 17 high-power fields (400×) of two to three synovial tissue sections, including deep sublining areas.