A human and a mouse anti-idiotypic antibody specific for human T14(+) anti-DNA antibodies reconstructed by phage display

Little is known about human anti-idiotypic antibodies. Phage display method ology was used to reconstruct these antibodies from lupus patients, which r ecognize a subset (T14(+)) of anti-DNA antibodies. Antigen-specific B cells were isolated from the blood using a peptide based on a complementarity de termining region (V(H)CDR3) of the prototypic T14(+) antibody, cDNA fragmen ts of the V-H and V-L genes prepared from the cells were expressed as phage displayed single chain Fv (scFv) fragments using the pCANTAB-5E phagemid v ector. From a reactive clone obtained, the Ig genes used were identified to be VH3, D5-D3, J(H)4b, VkappaI and J(kappa)2. The heavy chain was highly m utated, especially in CDR3, which bears mutations mostly of the replacement type; this region is also unusual in being extremely long due to a D-D fus ion. In contrast, a mouse hybridoma antibody, made to the same T14(+) pepti de and transformed as a scFv fragment, uses a short V(H)CDR3 comprising fiv e amino acids, three of which are tyrosines. Tyrosines may be important for antigen binding because two of these also exist in the human V(H)CDR3. The light chains of both antibodies may also contribute to the specificity of the protein, because their V-L segments, including the CDRs, are highly hom ologous to each other. (C) 2000 Elsevier Science B.V. All rights reserved.