Elevated synovial tissue concentration of the common acute lymphoblastic leukaemia antigen (CALLA)-associated neutral endopeptidase (3.4.24.11) in human chronic arthritis.

The cell-surface neutral endopeptidase 3.4.24.11 (NEP) activity of the common acute lymphoblastic leukaemia antigen (CALLA) cleaves diverse peptide mediators at specific sites and it has been postulated that it regulates immune responses. The concentration of NEP was quantified in detergent extracts of synovial tissues by the percentage hydrolysis of [3H-D-Ala]-Leu enkephalin/hr/100 mg of tissue. The synovial tissue concentration of NEP was higher in all patients with rheumatoid arthritis (n = 7; group mean +/- SD = 29.4 +/- 20.2%), and was higher with degenerative joint disease (n = 6 of 8; group mean +/- SD = 11.9 +/- 10.4%) than with traumatic arthropathy (n = 3; 1.1 +/- 0.7%). The lack of direct relationship between synovial tissue NEP concentration and leukocytic infiltration suggests that the cellular source of NEP may be synoviocytes or fibroblasts, and that NEP may have distinctive pathogenetic roles in human arthritis.