The acute phase response and its relation to amyloid A degrading activity in serum of patients with rheumatoid arthritis undergoing arthroplasty

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Abstract
The sequential changes in the concentration of specific serum proteins and their relation to amyloid A degrading activity were studied in 10 patients with rheumatoid arthritis undergoing arthroplasty of the knee of hip. Serum amyloid A protein increased from a preoperative level of 78 .+-. 20 gm/l (mean .+-. SEM [standard error of the mean]) to a peak level of 623 .+-. 93 mg/l on the 3rd postoperative day (P < 0.001). The serum amyloid A protein response was greater than that of any other protein including C-reactive protein, to which it was closely related (r = 0.84, P < 0.001). The concentrations of .alpha.1-antitrypsin and .alpha.1-antichymotrypsin were highest on the 4th postoperative day (mean changes + 35%, P < 0.01 and +44%, P < 0.05, respectively). Serum albumin, prealbumin and .alpha.2-macroglobulin behaved like negative acute phase reactants; the concentrations of albumin and .alpha.2-macroglobulin were significantly decreased from the 2nd-6th and 7th postoperative days, respectively, and the concentration of prealbumin was significantly decreased on the 3rd and 4th postoperative days. A significant fall in the amyloid A degrading activity of serum occurred during the acute phase reaction. The degradative activity was lowest on the 3rd and 4th postoperative days (P < 0.001). Apparently, the acute phase state in patients with rheumatoid arthritis induces a rise in the concentration of serum amyloid A protein, the putative serum precursor of tissue amyloid A fibrils and a concomitant reduction in the ability of serum to degrade these fibrils. These factors together may be important in the development of inflammation-associated amyloidosis.