IMMUNOLOGICAL MEASUREMENT OF TRANSFORMING-GROWTH-FACTOR-BETA-I (TGF-BETA-1) IN BLOOD - ASSAY DEVELOPMENT AND COMPARISON

Development of a new, sensitive immunoassay for measuring transforming growth factor beta 1 (TGF-beta 1) is described and compared with four commercially available TGF-beta 1 immunoassays. Preanalytical conditi ons were evaluated. The nonlinearity found in serum or plasma is due t o masking of TGF-beta 1 by binding proteins in blood. Mixing TGF-beta 1 with latency-associated peptide or alpha(2)-macroglobulin at physiol ogical concentrations suppressed most of the TGF-beta 1 signal. Plasma fibronectin showed no effect, even at concentrations exceeding its ph ysiological range. Equilibrium concentrations computed from a model sy stem confirmed the experimental results. Dilutional nonlinearity could be markedly reduced by an appropriately designed activation procedure that minimized the effects of reassociation between TGF-beta 1 and it s binding partners during restoration of a neutral pH. Plasma should b e used for measuring TGF-beta 1 in blood. Because serum TGF-beta 1 is highly significantly correlated with the platelet count, probably most of the TGF-beta 1 is released by platelet degranulation.