ABSTRACT
@EN We previously reported that IgG1 was the most important subclass containing TSH receptor blocking antibody activity but cleraly detectable blocking activity was found in the IgG2, IgG4, we tried to confirm the IgG subclass distribution of TSH
receptor blocking antibody activity by measuring the TSH binding inhibitory immunoglobulin in the purified IgG subclass fractions and by converting the TSH receptor bound blocking type IgG subclass to the stimulating type by antihuman IgG
antibody
(Fab
specific ) in rat thyroid (FRTL-5) cells.
From four patients wit primary nongoitrous hypothyroidism, sera containing TSH receptor blocking activity were separated into four IgG subclasses and non IgG fraction by deletion affinity chromatography using affinity columns of subclass specific
monoclonal antibodies. The TBII activities were dominant in IgG1 fractions in all four patients, but IgG2 and IgG4 fractions also showed significant TBII activities compared to non-IgG fractions iin 2 patients. The significant amount of cAMP
production
after the addition of goat antihuman IgG antibody (Fab specific) to the IgG subclass (TSH receptor blocking antibody) bound FRTL-5 cells was noted in IgG1, IgG2, IgG4 frations in case 1, in IgG1, IgG2 fractions in case 2, in IgG1 fraction in case
3, in
IgG1, Igg4 fractions in case 4.
These findings support the previous our study on the unrestricted IgG subclass distribution of TSH receptor blocking antibodies in primary nongoitrous hypothyroidism. (J Kor Endocrinol 8:164~170, 1993)
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