Intestinal absorption of proteinases triggers the formation of TGF-beta binding species of alpha2-macroglobulin in blood. Mediated by this process high concentrations of TGF-beta might be reduced via enhanced clearance of alpha2-macroglobulin-TGF-beta complexes. Thus, proteinase therapy may have beneficial effects in treatment of fibrosis and certain cancers accompanied by excessively high TGF-beta concentrations.

Background: Different molecular forms of prostatespecific antigen (PSA) have been used to differentiate between benign prostatic hyperplasia and prostate cancer. Detecting PSA bound to endogenous inhibitors such as ␣ 1 -antichymotrypsin (ACT) and ␣ 2 -macroglobulin (␣ 2 M) is often difficult because of epitope masking or sensitivity problems. Here we report the characterization of four novel mouse monoclonal antibodies (mabs) obtained by immunization with PSA-␣ 2 M complexes. Their ability to detect free PSA and PSA-inhibitor complexes was shown, and their epitopes were analyzed by phage display technology. Methods: The properties of the mabs were studied by competition and sandwich assays and by Western blotting. Epitope mapping was performed by screening of a phage display peptide library. Results: All four mabs recognized free PSA, PSA-ACT, and PSA-␣ 2 M complexes, but to various degrees. With different combinations of mabs in competition experiments, antibodies were identified that enhance binding of other mabs to PSA, forming the molecular basis of a very sensitive assay for the detection of PSA and PSA-ACT complexes. Mabs with highest reactivity for PSA-␣ 2 M were selected to establish an immunoassay for that complex. Western blot analysis revealed that all mabs recognized conformational epitopes of PSA. These findings were supported by phage display results demonstrating mimotopes in the PSA molecule.