Antitrypsin activity and enzyme inhibitors in the rheumatoid joint.

Proteolytic enzyme inhibitor activity has been measured in the rheumatoid knee by 2 different techniques. The inactivation rate of trypsin injected into the joint in 13 patients was compared with synovial fluid levels of alpha-1-antitrypsin (apha 1AT), alpha-2-macroglobulin (alpha 2M) and trypsin inhibitory capacity (TIC). The lack of correlation and the fact that an inverse relationship was shown between the T1/2 to inactivation and joint damage suggests that additional mechanisms are involved in the inactivation of destructive enzymes. Serum levels of alpha 1AT and TIC were elevated in 36 rheumatoid arthritis (RA) patients when compared with control values and RA synovial fluid inhibitor levels elevated by comparison with osteoarthritic figures. The synovial fluid alpha 1AT and TIC correlated with the activity of the lysosomal enzyme beta-acetyl glucosaminidase (beta AGA) but only trace amount of neutral protease activity was detected probably because of the large concentration of inhibitors present. The deficient Pi phenotype MZ was rarely encountered.