D-DIMERS ARE DEGRADED BY HUMAN NEUTROPHIL ELASTASE

To see if D-dimers were degraded by human neutrophil elastase (HNE), c ross-linked fibrin was obtained by adding thrombin to purified fibrino gen in the presence of calcium ions and factor XIII, and the fibrin cl ot subsequently degraded by plasmin. Thereafter, the supernatant conta ining fibrin degradation products was removed and incubated with HNE. D-dimer levels were measured by two rapid semiquantitative tests, a la tex agglutination test and the Nycocard immunofiltration test, and a q uantitative ELISA-method. With increasing incubation time, D-dimer lev els as measured by the latex and Nycocard tests rapidly decreased and subsequently became undetectable, while the ELISA D-dimer values remai ned essentially unchanged. By using SDS-electrophoresis and immunoblot ting, the degradation of plasmic derivatives of cross-linked fibrin by HNE was visualised. We conclude that in a purified system, D-dimers f ormed during plasmin mediated lysis of cross linked fibrin are further degraded by HNE. Such HNE degradation reduces the D-dimer concentrati on as measured by rapid semiquantitive tests, and may be partly respon sible for discrepant results when using different D-dimer assays.