Sensitive thyroid-stimulating antibody assay in whole serum containing five percent polyethylene glycol using porcine thyroid cells

Previously we reported that the amounts of cyclic adenosine monophosphate ( cAMP) production by polyethylene glycol (PEG) 22.5% precipitated fraction ( PF) (crude immunoglobulin G [IgG]) from thyroid-stimulating antibody (TSAb) -positive serum were higher than those by PEG 12.5% PF, and that PEG (5%) a ugmented affinity purified TSAb-IgG-stimulated cAMP production in porcine t hyroid cells (PTC) assay. In the present work, we studied sensitive TSAb as say using whole sera in the presence of high PEG concentrations in PTC assa y. cAMP produced by TSAb-positive serum increased in proportion to serum am ounts up to 0.05 mL,but gradually decreased in 0.075 mL. The maximal augmen tative effect of PEG on TSAb-positive serum (0.05 mL)-stimulated cAMP produ ction was found in 5% PEG (final). Thus, TSAb assay using whole serum (0.05 mL) in the absence of 5% PEG (serum method) and sensitive TSAb (sTSAb) ass ay using whole serum (0.05 mL) in the presence of 5% PEG (;serum plus 5% PE G method) were performed. The sensitive thyroid-stimulating antibody (sTSAb ) activities of Graves' sera showed significantly higher (twofold to sevenf old) compared to simple TSAb activity with sera, sTSAb and TSAb activities were positive in 91% (29/32) and 47% (15/32) of untreated Graves' patients with hyperthyroidism. The sTSAb activities by serum plus 5% PEG method were higher than that by PEG 12.5% precipitated fraction (PF) from test serum ( 0.2 mL) in many Graves' sera, but lower than that by PEG 22.5% PF from test serum (0.2 mt). PEG (5%) did not augment cAMP produced by high TSH serum ( 127-210 mU/L) in thyroiditis chronica. sTSAb activity was negative in adeno matous goiter, subacute thyroiditis, and thyroid cancer. sTSAb activity was also negative in TSH stimulation blocking antibody (TSBAb)positive hypothy roidism (during thyroxine [T-4] treatment), but was positive in Graves' ser a with coexistence serum of TSAb and TSBAb because of augmentative effect o f 5% PEG on TSAb activity. This assay in whole serum (0.05 mL) containing 5 % PEG is less sensitive than sensitive TSAb assay using PEG 22.5% PF from t est serum (0.2 mL), but this method can be available clinically as routine TSAb assay using whole serum because of the technical simplicity.