Characterization of antibodies to prostate-specific antigen

Antibodies submitted to the ISOBM TD-3 PSA Workshop were tested for reactiv ity with free prostate-specific antigen (PSA) and the PSA alpha(1)-antichym otrypsin (ACT) complex, inhibition of proteolytic activity, recognition of continuous epitopes, and epitope specificity based on complete cross-inhibi tion studies. The antibodies could be separated into two categories: those recognizing hidden epitopes specific for free PSA, and those recognizing ep itopes in both free PSA and the PSAACT complex. A large number of distinct antigenic domains were identified both in free PSA and the PSA-ACT complex.