Binding of autoantibodies to a synthetic peptide with residues His2009 to Val2018.
(A) Direct binding of autoantibodies to peptide His2009-Val2018. Serial dilutions of autoantibody F(ab′)2 were added to immobilized peptide (100 μM). Bound F(ab′)2 was detected with using peroxidase-conjugated goat-antihuman IgG4F(ab′)2. Case 1, ○; case 2, ●; case 3, ■; type 1 autoantibody F(ab′)2, ▪. (B) Inhibitory effects of peptide His2009-Val2018 on autoantibody binding to 80-kd LCh. Serial dilutions of synthetic peptide were incubated with 1 μM autoantibody F(ab′)2 for 2 hours at 37°C before being added to immobilized 80-kd LCh (60 nM). Case 1, ○; case 2, ●; case 3, ■; type 1 autoantibody F(ab′)2, ▪. (C) Inhibitory effects of both peptide Lys1804-Val1819 and peptide His2009-Val2018 on autoantibody binding to 80-kd LCh. The mixtures of serial dilutions of both peptides were incubated with 1 μM autoantibody F(ab′)2 for 2 hours at 37°C before being added to immobilized 80-kd LCh (60 nM). Case 1, ○; case 2, ●; case 3, ■.
