Cross-reactivity of ten anti-prostate-specific antigen monoclonal antibodies with human glandular kallikrein

Prostate-specific antigen (PSA) is commonly used as a marker for prostate disease. Prostate epithelium expresses both PSA and human glandular kallikrein (hK2) proteins, which share 80% sequence homology. The immunologic cross-reactivity of these two proteins could potentially interfere with determination of PSA levels in diagnoses of prostate cancer. We set out to determine the extent of this cross-reactivity for a panel of 10 anti-PSA monoclonal antibodies (mAbs). Enzyme-linked immunosorbent assay (ELISA), sandwich assays, and western transfer techniques were used to assess the PSA/hK2 cross-reactivity of the anti-PSA mAbs. We did not detect the hK2 protein with any of the 10 anti-PSA mAbs under western transfer conditions. In ELISA experiments, 8 of 10 mAbs exhibited hK2 cross-reactivity under certain conditions. However, no combination of mAbs tested in sandwich assays exhibited a signal in hK2 cross-reactivity experiments greater than 0.1 % of the PSA signal. We have evaluated 10 anti-PSA mAbs and determined that despite the 80% homology between However, no combination of mAbs tested in sandwich assays exhibited a signal in hK2 cross-reactivity experiments greater than 0.1 % of th PSA and hK2 proteins, cross-reactivity with hK2 by these antibodies would not significantly affect the determination of PSA levels by means of sandwich assays.