Elastolytic activity of human blood monocytes characterized by a new monoclonal antibody against human leucocyte elastase. Relationship to rheumatoid arthritis.

The leucocyte elastase of human blood monocytes was investigated by applying a new monoclonal antibody which did not block the enzyme activity against elastin. In a fixed population of mononuclear cells (MNC) and using fluorescence activated cell sorting (FACS), the human leucocyte elastase (HLE) antibody identified a subgroup of CD14+ cells which contained all the elastase activity and which could be blocked by a specific chloromethylketone elastase inhibitor. By anti-CD14 labelling the HLE positive cells were identified as monocytes and amounted to 88% of this cell type (median: range 72-96%). In a parallel study of patients with active rheumatoid arthritis (RA) and control donors the elastolytic capacity of PMA-stimulated live MNC was higher for RA patients than for controls (p less than 0.02). For control donors the number of HLE+ cells correlated well to the elastolysis in the same MNC sample (Spearman's rho:0.83, p less than 0.05); in the samples from RA patients no correlation was found between the normal number of HLE+ cells and the increased elastolysis (rho: 0.54, p greater than 0.20).