The critical concentration of C1-esterase inhibitor (C1-INH) in human serum preventing auto-activation of the first component of complement (C1).
C1-esterase inhibitor (C1-INH) was depleted from normal human serum (NHS) at 4 degrees C by affinity chromatography with a monoclonal anti-C1-INH antibody (mAb 13 E1) coupled to CNBr-activated Sepharose 4B. The C1-INH-depleted serum (C1-INH-depl-HS) had normal levels of C1, C4, and CH 50 and C1-INH concentration was less than 10% of normal (15 microg/ml in C1-INH-depl-HS compared to 230 microg/ml in NHS). C1-auto-activation in C1-INH-depl-HS was followed by measuring C4-consumption in a haemolytic assay and by detection of activated C1s in a C1s-ELISA. After a lag phase of 10-20 min, C1-auto-activation in C1-INH depl-HS occurred and reached its maximum after 40 min at 37 degrees C. In contrast, neutralization of C1-INH activity in NHS by addition of monoclonal antibodies directed against its C1s-binding site, resulted in an immediate, spontaneous C1-activation without a lag-phase and reached its maximum already after 20 min (mAb 140) and 25 min (mAb 88G2). Addition of highly purified C1-INH or NHS as source of C1-INH to C1-INH-depleted serum to a final concentration of 55 microg/ml (22% of normal C1-INH concentration in HS) was sufficient to control spontaneous C1-activation.
Windfuhr
Jochen P
JP
Institute of Medical Microbiology and Hygiene, Johannes Gutenberg-University Mainz, Hochhaus am, Augustusplatz, 55101 Mainz, Germany. jwindfuhr@aol.com
Alsenz
Jochem
J
Loos
Michael
M
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D003172:Complement C1 / Q000276:immunology / Q000378:metabolism*; D003174:Complement C1 Inactivator Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D044967:Serum / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D003172:Complement C1; D003174:Complement C1 Inactivator Proteins