VH and V kappa segment structure of anti-insulin IgG autoantibodies in patients with insulin-dependent diabetes mellitus. Evidence for somatic selection.

摘要: In some patients with insulin-dependent (type I) diabetes mellitus (IDDM), autoantibodies to insulin are present at diagnosis. After initiation of the treatment not only animal but also human insulin, anti-insulin, mainly IgG, become a major component autoimmune response in virtually all IDDM patients. Their structure, however, is still relatively unknown. We analyzed structure VH and V kappa segments three IgG mAb derived from The sequences genes two mAb13 mAb48, were 98.3 96.6% identical those H11 1.9III (VHIII family), respectively. sequence gene third mAb49, was 98.6% that 51p1 (VHI family). All used III segments. mAb49 97.9 98.9% identical, respectively, kv3g gene; mAb48 96.5% kv328 gene. and/or these anti-insulin similar Ig expressed fetal, adult normal B cell repertoires. nucleotide differences displayed by sequences, when compared closest reported germ-line genes, concentrated CDR (6.2 x 10(-2) 0.8 difference/base FR, respectively; p < 0.01, chi 2 test), yielded significantly higher putative replacement (R) silent (S) mutation ratio (12.0) than framework (0.2). concentration their high R:S ratios consistent hypothesis underwent process somatic Ag-driven clonal selection. That such constituted point-mutations formally proved mAb13, differentially targeted PCR amplification Southern blot hybridization mAb13-producing line DNA. gave rise segment cloned using genomic DNA PMN same patient whose cells for generation this mAb. Overall, (putative verified) 27 amino acid replacements, which 14 nonconserved. Four resulted positively charged residues, Arg one His.(ABSTRACT TRUNCATED AT 400 WORDS)