Novel detection method for human protein C inhibitor (PCI) using immunoblotting with antibodies specific to synthetic peptides corresponding to the N-terminal and C-terminal amino acid sequences of human PCI.

Three types of antibody, which were specific to the purified human protein C inhibitor (PCI) and to two synthetic peptides, which corresponded to the N-terminal 15 amino acid residues (PCI-N) and C-terminal 15 residues (PCI-C) of PCI, were produced. Plasma PCI patterns, which were shown by means of polyacrylamide gel isoelectric focusing followed by immunoblotting with the antibody to purified PCI, were almost identical to those obtained with the antibodies to the peptides, PCI-N and PCI-C. The latter antibodies against the synthetic peptides proved very useful for biochemical or genetic analysis of human plasma PCI, as such peptide antigens could be produced without any of the tedious procedures necessary to obtain purified PCI as an immunogen.