Lactoferrin and lysozyme in arthritic exudates.

Lactoferrin (LF) has been assayed by radioimmunoassay in plasma and arthritic exudates and compared with lysozyme (LZ) levels and leukocyte counts. The mean LF concentration in 38 rheumatoid arthritis (RA) exudates was 9.1 mg/l (range 0.02-39.2). In 30 non-RA exudates LF was 3.3 mg/l (range 0.01-14.6). The corresponding LZ levels were 7.4 mg/l (range 2.5-18.5) in RA and 4.7 (range 1.0-12.5) in non-RA fluids. Exudate/plasma ratios were much higher for LF than for LZ and higher in RA than in non-RA exudates, whereas leukocyte counts did not differ. The LF/leukocyte count ratio was significantly higher in RA than in the non-RA group. The data suggest a more prominent release of neutrophilic granulocyte components in RA than in non-RA arthritis.