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SR Reddigari and AP Kaplan
Department of Medicine, SUNY, Stony Brook 11794-8161.
We developed a mouse monoclonal antibody (MoAb 115-21) to human high-
molecular-weight kininogen (HK) that recognizes its prekallikrein binding
site (residues 565 through 595 of HK). The corresponding synthesized
31-amino acid peptide (peptide IV) was recently shown to retain native HK's
prekallikrein binding property. The same peptide bound factor XI also,
although less avidly. Our MoAb recognizes purified HK, peptide IV, and the
light chain moiety of HK (where the peptide IV resides), as shown by
enzyme-linked immunosorbent assay (ELISA) and Western blotting experiments.
The apparent dissociation constant for the HK and MoAb 115-21 interaction
was 2.2 nmol/L. It does not recognize low-molecular-weight kininogen (LK)
with which HK shares its heavy chain moiety or any antigens in human plasma
congenitally deficient in kininogens. The binding of MoAb 115-21 to
purified light chain of HK was competitively inhibited by peptide IV. In
addition, the antibody inhibits HK-dependent clotting activity of normal
human plasma and dextran sulfate-mediated activation of prekallikrein in
plasma and retards cleavage of HK in normal plasma after contact activation
with dextran sulfate. Also, purified Fab fragments of MoAb 115-21 inhibited
the HK-dependent coagulant activity and dextran sulfate-mediated
prekallikrein activation in normal plasma. Since the kd for HK-MoAb 115- 21
interaction is ten times lower than that of HK-prekallikrein, our data
suggest that binding of MoAb 115-21 to HK's peptide IV site increases the
free prekallikrein concentration in plasma and thus results in the
decreased efficiency of factor XIIa-mediated activation of prekallikrein.
Decreased levels of kallikrein thus formed may be responsible for the
inhibition of HK-dependent clotting activity and the decrease in rate and
extent of HK cleavage in normal plasma on contact activation with dextran
sulfate. MoAb 115-21 may thus prove very useful, especially with its high
affinity for HK, in further delineation of the role of HK and prekallikrein
in contact activation and kinin-related human pathology.
This article has been cited by other articles:
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| Copyright © 1989 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
