REPERTOIRE CLONING OF LUPUS ANTI-DNA AUTOANTIBODIES

To investigate the autoantibody repertoire associated with SLE, we hav e created phage display IgG Fab libraries from two clinically active S LE patients and from the healthy identical twin of one of these patien ts. The libraries from the lupus discordant twins were found to both i nclude unusually large representations of the V(H)5 gene family. By pa nning with DNA, the SLE libraries each yielded IgG anti-doublestranded (ds) DNA autoantibodies, which are characteristic of lupus disease. T hese included a V(H)5 autoantibody from the affected twin, that has a targeted cluster of mutations that potentially improves binding affini ty. The recovered IgG anti-dsDNA autoantibodies expressed the same idi otypes associated with the in vivo. IgG anti-dsDNA response of the res pective SLE donor. Heavy-light chain shuffling experiments demonstrate d a case in which the in vitro creation of anti-dsDNA binding activity required restrictive pairing of a heavy chain with V-lambda light cha ins similar to those in circulating anti-dsDNA autoantibodies. By cont rast, IgG anti-ds autoantibodies could not be recovered from the libra ry from the healthy twin, or from shuffled libraries with heavy chains from the healthy twin. These repertoire analyses illustrate how inher itance and somatic processes interplay to produce lupus-associated IgG autoantibodies.