Recombinant thyroid peroxidase-specific autoantibodies. I. How diverse is the pool of heavy and light chains in immunoglobulin gene libraries constructed from thyroid tissue-infiltrating plasma cells.
Thyroid peroxidase (TPO) autoantibodies are a distinguishing feature of autoimmune thyroid disease. We have previously constructed immunoglobulin G heavy (H) and light (L) chain cDNA libraries from intrathyroidal B-cells. TPO-selected autoantibodies expressed by combined H and L chain libraries (combinatorial libraries) recognized a limited number of epitopes on TPO and used only a few of the many H and L chain variable region genes present in the genome (germline genes). One possible explanation for this restriction is a lack of diversity in the parental H and L chain gene libraries used to construct the combinatorial library. To address this issue, we determined the nucleotide sequences of randomly selected H and kappa L chain variable region genes from a pair of H and L chain libraries. The 12 H chain gene sequences analyzed were highly diverse, and none resembled the genes of TPO-selected autoantibodies. The sequences of 14 randomly selected kappa L chain genes were less diverse; 12 of 14 were closely related to the same germline gene (KL012) used by TPO-specific autoantibodies. However, we observed previously that only about 1 in 500 of the L chains in this library can pair with an H chain and bind TPO. We now find that, with 1 exception, the randomly selected KL012-like genes in the L chain library differ significantly from the antigen-specific KL012-like genes, particularly in the antigen-binding regions. In summary, the present data indicate that 1) the restricted number of H chain genes used by TPO-specific autoantibodies cannot be ascribed to limited H chain gene diversity in the parent library; and 2) L chains from combinatorial libraries (even when related to the same germline gene) cannot simply be regarded as plastic, or promiscuous, partners for high affinity antigen binding by a particular H chain.
Thyroid Molecular Biology Unit, Veterans Administration Medical Center, San Francisco, California 94121.
J C
JC
Jaume
G
G
Costante
S
S
Portolano
S M
SM
McLachlan
B
B
Rapoport
D000595:Amino Acid Sequence; D000918:Antibody Specificity; D000941:Antigens / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D001483:Base Sequence; D002465:Cell Movement; D015723:Gene Library; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000235:genetics*; D007453:Iodide Peroxidase / Q000276:immunology*; D008969:Molecular Sequence Data; D010950:Plasma Cells / Q000502:physiology*; D011994:Recombinant Proteins; D013961:Thyroid Gland
D000941:Antigens; D001323:Autoantibodies; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007136:Immunoglobulins; D011994:Recombinant Proteins; D007453:Iodide Peroxidase