Calprotectin (the LI protein) during surgery in patients with rheumatoid arthritis

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Abstract
Calprotectin (LI) is a major leukocyte protein which is released during activation or death of neutrophil granulocytes and monocytes. Previous studies have shown that LI may be a useful marker of disease activity in patients with adult or juvenile rheumatoid arthritis (RA). In the present study, the plasma concentrations of LI were analysed during shoulder-joint surgery in 16 patients with adult or juvenile RA. Decreased LI concentrations were found 48 h postoperatively. Thereafter, the LI concentrations were increased at 72 h, with a following decrease until day 14 postoperatively. In contrast, increased serum concentrations of both C-reactive protein (CRP) and orosomucoid (i.e. a,-acid glycoprotein) were found at 48 h after surgery. Plasma samples obtained before and after surgery were analysed by gel filtration. Approximately 3/4 of the plasma LI was found in fractions corresponding to the native molecule, while the rest was detected in higher molecular mass fractions. The distribution of LI antigen in low and high molecular mass regions did not differ between the pre-and postoperative plasma samples. The LI protein consists of light and heavy chains. Increased serum levels of the cystic fibrosis antigen, which is identical to LI light chain, have been described in patients with cystic fibrosis. The existence of circulating free LI chains was presently investigated in plasma obtained before and after surgery. After gel filtration of plasma samples, no free LI chains were detected by use of enzyme immunoassay and dot blot.