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The I binding specificity of human VH 4-34 (VH 4-21) encoded antibodies is determined by both VH framework region 1 and complementarity determining region 3.

Abstract：

:Essentially all cold agglutinins (CA) with red blood cell I/i specificity isolated from patients with CA disease stemming from lymphoproliferative disorders utilize the VH 4-34 (VH 4-21) gene segment. This near universality of the restricted use of a single gene segment is substantially greater than that demonstrated for other autoantibodies. The monoclonal antibody 9G4 exclusively binds VH 4-34 encoded antibodies and serves as a marker for the VH 4-34 gene segment. Previous studies form our laboratory localized the 9G4 reactive area to framework region 1 (FR1). In the present study, the relative roles of VH FR1, heavy (H) chain complementarity determining region 3 (CDRH 3) and the light (L) chain in I antigen binding were investigated. Mutants containing FR1 sequences from the other VH families, CDRH 3 exchanges, and combinatorial antibodies involving L chain interchanges were produced in the baculovirus system and tested in an I binding assay. The data indicate that FR1 of the VH 4-34 gene segment and the CDRH 3 are essential for the interaction between CA and the I antigen, with the CDRH 3 being fundamental in determining the fine specificity of antigen binding (I versus i). Mutants with substantially altered CDRH 1 and CDRH 2 regions bind I as long as the FR1 is VH 4-34 encoded and the CDRH 3 has a permissive sequence. Light chain swaps indicate that even though antigen binding is predominantly mediated by the H chain, the association with antigen can be abrogated by an incompatible L chain. The necessity for VH 4-34 FR1 explains the almost exclusive use of the VH 4-34 gene segment in cold agglutinins. We hypothesize that, as a general phenomenon, the H chain FR1 of many antibodies may be important in providing the contact required for the close association of antibody with antigen, while the CDRH 3 dictates the fine specificity and strenght of binding.

journal_name

J Mol Biol

journal_title

Journal of molecular biology

authors

Li Y,Spellerberg MB,Stevenson FK,Capra JD,Potter KN

doi

10.1006/jmbi.1996.0110

subject

Has Abstract

pub_date

1996-03-01 00:00:00

pages

577-89

issue

eissn

0022-2836

issn

1089-8638

pii

S0022283696901102

journal_volume

256

pub_type

杂志文章

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The I binding specificity of human VH 4-34 (VH 4-21) encoded antibodies is determined by both VH framework region 1 and complementarity determining region 3.