Monoclonal antibody FDC-6 exhibits binding to human plasma fibronectin: a caveat for cervicovaginal oncofetal fibronectin testing?
OBJECTIVE
Monoclonal antibody FDC-6 has been used clinically to measure cervicovaginal fibronectin and to predict patients at risk for preterm labor. Because bleeding is often a complicating factor during pregnancy, the aim of this study was to determine whether FDC-6 reactive fibronectin is present in normal human plasma.


METHODS
Quantitative Western immunoblots and a commercially available enzyme-linked immunosorbent assay were used to measure FDC-6 binding to nonpregnant human and bovine plasma fibronectin. FDC-6 binding to whole sera was also assessed, as was the effect of enzymatic deglycosylation of human plasma fibronectin.


RESULTS
Both assays demonstrated measurable FDC-6-reactive fibronectin in nonpregnant human blood, with plasma concentrations ranging from 3 to 12 micrograms/ml (1% to 4% of total plasma fibronectin). FDC-6 had no detectable binding activity to bovine plasma fibronectin. De-O-glycosylated human plasma fibronectin had markedly reduced binding activity for FDC-6.


CONCLUSIONS
FDC-6 binds specifically to a clinically significant percentage of circulating O-glycosylated human plasma fibronectin isoforms that are not associated with pregnancy. This caveat should be considered when pregnant patients are evaluated for the presence of FDC-6 reactive oncofetal fibronectin in the cervix or vagina.
Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, Philadelphia 19104-4283.
R F
RF
Feinberg
C L
CL
Wang
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015153:Blotting, Western; D002417:Cattle; D002584:Cervix Uteri / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005353:Fibronectins / Q000276:immunology / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007536:Isomerism; D008297:Male; D014621:Vagina / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D005353:Fibronectins