Modulations of anti-D affinity following promiscuous binding of the heavy chain with naïve light chains

Authors

  • Isabelle St-Amour,

    1. From the R&D Department, HÉMA-QUÉBEC, Sainte-Foy, Québec;
    2. Department of Biochemistry and Microbiology, Science Faculty, Laval University, Québec, Canada.
    Search for more papers by this author
  • Chantal Proulx,

    1. From the R&D Department, HÉMA-QUÉBEC, Sainte-Foy, Québec;
    2. Department of Biochemistry and Microbiology, Science Faculty, Laval University, Québec, Canada.
    Search for more papers by this author
  • Réal Lemieux,

    1. From the R&D Department, HÉMA-QUÉBEC, Sainte-Foy, Québec;
    2. Department of Biochemistry and Microbiology, Science Faculty, Laval University, Québec, Canada.
    Search for more papers by this author
  • Renée Bazin

    1. From the R&D Department, HÉMA-QUÉBEC, Sainte-Foy, Québec;
    2. Department of Biochemistry and Microbiology, Science Faculty, Laval University, Québec, Canada.
    Search for more papers by this author

  • ABBREVIATIONS:

    CDR(s) = complementarity-determining region(s); H chain = heavy chain; L chain = light chain; pI = isoelectric point.

Address reprint request to: Renée Bazin, PhD, R&D Department, HÉMA-QUÉBEC, 2535 Boulevard Laurier, Sainte-Foy, Québec, Canada, G1V 4M3; e-mail: Renee.Bazin@hema-quebec.qc.ca .

Abstract

BACKGROUND : It is generally accepted that the antibody heavy (H) chain is more important than the light (L) chain for determining antigen specificity. In the case of anti-D, the predominant role of H chains in antigen binding is well recognized, but much less is known about the function of L chains. In this work, the contribution of L chains from non-D-immunized donors to the specificity and reactivity of anti-Ds was studied with L-chain shuffling.

STUDY DESIGN AND METHODS : A kappa L chain library was recombined with the H chain of the 43F10 anti-D in a phagemid vector system (pComb3H, Scripps Institute). D-specific F(ab) phages were selected by panning on RBCs. Soluble F(ab)s were prepared, and their reactivity was assessed by RBC agglutination. The nucleotide and amino acid sequences of the variable region of the L chains were analyzed.

RESULTS : The L chains of the six D-specific 43F10 F(ab) clones studied used five different germline genes from three Vκ families and three different Jκ segments. The L chains were all cationic with isoelectric points ranging from 8.1 to 10.2.

CONCLUSION : The 43F10 anti-D H chain could bind promiscuously to a diversity of L chains from non-D-immunized donors without losing the D-antigen specificity. Relationships between the anti-D affinity and the cationic charge of the L chain as well as with the presence of an arginine residue in the L-chain complementarity-determining region 1 were observed.

Ancillary