1993 Volume 22 Issue 1 Pages 42-48
Non-linearity in the enzyme immunoassay system for γ-seminoprotein (γ-Sm), Chugai Seiyaku Co., was previously frequently observed for series of diluted patient samples having elevated γ-Sm levels. This was greatly improved by using diluted seurm, inactivated serum, or a two-step modification of the system. The inhibition is presumably the result of the following: since the assay system uses a common one-step sandwich method, γ-Sm and some constituents in serum, possibly including prostate specific antigen (PSA), equally react with enzyme-labeled anti-γ-Sm antibody in the 2nd step of the antigen-antibody reaction. The titer of γ-Sm assayed is then falsely low dye to lack of the labeled reagent. Fairly good linearity was obtained in a recently improved assay system making use of decreased sample volumes and increased labeled antibody. The results of HPLC gel filtration demonstrated that the molecular weight for γ-Sm was mainly 34KD which was in agreement with that described earlier reports, and the fractions for PSA were divided into two portions corresponding to their molecular weights of 34KD and 120KD. The PSA fraction of the 120KD portion inhibited the γ-Sm reaction.
