Autoantigenic determinants on human thyroglobulin. I. Determinant specificities of murine monoclonal antibodies.

To map the antigenic determinants, a panel of 20 mouse monoclonal antibodies (mAbs) to native human thyroglobulin (Tg) was generated. Four criteria were established for distinguishing the determinants recognized by the various mAbs: (i) reactivity to Tgs from eight different species; (ii) reactivity to oxidized and reduced human Tg; (iii) the ability of thyroxine to inhibit binding of mAbs; and (iv) the pattern of antigenic determinant reactivity as determined in reciprocal competitive inhibition binding assays. Of 20 mAbs examined, 12 bound only to human Tg, 3 bound to all eight species tested, and 5 bound to human Tg and to Tg from at least one of the other seven species. Eight mAbs bound oxidized/reduced and native human Tg equally well, 2 bound to the oxidized/reduced protein better than to the native, 7 showed virtually no reactivity to oxidized/reduced human Tg, and 3 others reacted to the oxidized/reduced protein significantly less than they bound to the native. The binding of 5 mAbs to native human Tg was inhibited by thyroxine. The pattern of shared determinant specificities revealed that at least 12 determinant clusters were defined by the panel of mAbs. Among the 12 determinant clusters were 3 designated as immunodominant; 8 of 20 mAbs defined these immunodominant clusters. The four criteria taken together indicate that at least 19 different epitopes on human Tg could be distinguished by this panel of mAbs. These mAbs are useful for the study of determinant specificities of Tg autoantibodies in humans.