Prostate-specific antigen in serum occurs predominantly in complex with alpha 1-antichymotrypsin.
Immunologic measurements of the serum concentration of prostate-specific antigen (PSA), an abundant prostatic-secreted serine proteinase, are frequently used to monitor patients with prostate cancer, though it has not been ascertained whether this immunoreactivity represents a PSA zymogen, the active proteinase, or PSA complexed to extracellular proteinase inhibitors. To characterize the PSA immunoreactivity in serum, we used monoclonal antibodies produced against PSA and a polyclonal rabbit IgG against alpha 1-antichymotrypsin in the design of three noncompetitive PSA assays: assay T, which detected PSA both when present as the active proteinase and when complexed to alpha 1-antichymotrypsin; assay F, which recognized the active proteinase but most poorly detected PSA complexed to alpha 1-antichymotrypsin; and assay C, which was specific for PSA complexed to alpha 1-antichymotrypsin. We used the three assays to measure PSA immunoreactivity in 64 patients' sera and in the effluent after gel chromatography of sera from four patients. This identified an 80- to 90-kDa complex between PSA and alpha 1-antichymotrypsin as the predominant fraction of the PSA immunoreactivity in blood plasma; an immunoreactive 25- to 40-kDa compound was the minor fraction.
Lilja
H
H
Department of Clinical Chemistry, University of Lund, Malmö General Hospital, Sweden.
Christensson
A
A
Dahlén
U
U
Matikainen
M T
MT
Nilsson
O
O
Pettersson
K
K
Lövgren
T
T
D000818:Animals; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000097:blood* / Q000276:immunology; D014408:Biomarkers, Tumor / Q000097:blood*; D002850:Chromatography, Gel; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017430:Prostate-Specific Antigen; D000514:alpha 1-Antichymotrypsin / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D000939:Epitopes; D000514:alpha 1-Antichymotrypsin; D017430:Prostate-Specific Antigen