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

The sequential changes in the concentration of specific serum proteins and their relation to amyloid A degrading activity were studied in ten patients with rheumatoid arthritis undergoing arthroplasty of the knee or hip. Serum amyloid A protein increased from a preoperative level of 78 +/- 20 gm/l (mean +/- SEM) to a peak level of 623 +/- 93 mg/l on the third postoperative day (P less than 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 less than 0.001). The concentrations of alpha 1-antitrypsin and alpha 1-antichymotrypsin were highest on the fourth postoperative day (mean changes + 35%, P less than 0.01, and +44%, P less than 0.05, respectively). Serum albumin, pre-albumin and alpha 2-macroglobulin behaved like negative acute phase reactants; the concentrations of albumin and alpha 2-macroglobulin were significantly decreased from the second to sixth and seventh postoperative days, respectively, and the concentration of pre-albumin was significantly decreased on the third and fourth 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 third and fourth postoperative days (P less than 0.001). The results show that 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.