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


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 Vkappa families and three different Jkappa segments. The L chains were all cationic with isoelectric points ranging from 8.1 to 10.2.


CONCLUSIONS
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.
St-Amour
Isabelle
I
R&D Department, HEMA-QUEBEC, Sainte-Foy, Québec, USA.
Proulx
Chantal
C
Lemieux
Réal
R
Bazin
Renée
R
D000915:Antibody Affinity; D000918:Antibody Specificity; D001483:Base Sequence; D002412:Cations; D022801:Complementarity Determining Regions / Q000737:chemistry / Q000276:immunology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000276:immunology / Q000378:metabolism*; D007147:Immunoglobulin Light Chains / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007518:Isoantibodies / Q000276:immunology*; D008969:Molecular Sequence Data; D019151:Peptide Library; D011485:Protein Binding; D012204:Rh-Hr Blood-Group System / Q000276:immunology; D018029:Rho(D) Immune Globulin
D002412:Cations; D022801:Complementarity Determining Regions; D007140:Immunoglobulin Fab Fragments; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007518:Isoantibodies; D019151:Peptide Library; C061961:RHO(D) antibody; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin; C026410:Rho(D) antigen