An enzyme-linked immunosorbent assay for human cathepsin X, a potential new inflammatory marker.
The human lysosomal cysteine-type carboxypeptidase cathepsin X is mainly present in monocytes and macrophages and may be released into the circulation due to constitutive and/or regulated secretion by (activated) immune cells. To define its potential diagnostic value as an inflammatory marker, we have developed a highly sensitive and specific sandwich-type immunoassay (ELISA) for cathepsin X permitting both intra- and extracellular detection and quantification. The dynamic range of the cathepsin X ELISA was determined to be 100 (detection limit) to 8000 pg/ml. Reproducibility of both within and between runs yielded coefficients of variation (CVs) of 2.7-3.5% and 6.3-7.3%, respectively. Cross-reactivity with other members (cathepsin B, L) of the thiol-dependent cathepsin family was not observed. The ELISA was used to quantify cathepsin X in leukocytes as well as in plasma of healthy volunteers and patients with multiple trauma. During the first 72 h after trauma, plasma levels of cathepsin X increased significantly, particularly in patients who died during the posttraumatic period. In comparison to the well-known inflammation marker neutrophil elastase, cathepsin X levels predicted survival with a higher significance in the later posttraumatic phase. In conclusion, this report provides the first evidence of cathepsin X immunoreactivity not only in cell lysates but also in plasma samples. We suggest that the newly developed highly reproducible ELISA will be of great value for further evaluation of this protease as a diagnostic and/or prognostic marker in inflammatory diseases.
Nägler
Dorit K
DK
Department of Clinical Chemistry and Clinical Biochemistry, University Hospital of Surgery-City, Ludwig-Maximilians-University, Nussbaumstr. 20, 80336 Munich, Germany. dorit.naegler@med.uni-muenchen.de
Lechner
Annette M
AM
Oettl
Annemarie
A
Kozaczynska
Karolina
K
Scheuber
Heinz-Peter
HP
Gippner-Steppert
Cornelia
C
Bogner
Viktoria
V
Biberthaler
Peter
P
Jochum
Marianne
M
D000818:Animals; D001774:Blood Chemical Analysis / Q000379:methods; D016022:Case-Control Studies; D056657:Cathepsin K; D002403:Cathepsins / Q000032:analysis* / Q000097:blood / Q000235:genetics / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D018836:Inflammation Mediators / Q000032:analysis*; D019272:Leukocyte Elastase / Q000032:analysis; D007962:Leukocytes / Q000201:enzymology; D010865:Pilot Projects; D011817:Rabbits; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D014947:Wounds and Injuries / Q000097:blood
D018836:Inflammation Mediators; D011994:Recombinant Proteins; D002403:Cathepsins; D019272:Leukocyte Elastase; C534130:CTSK protein, human; D056657:Cathepsin K