Immunogenetic analysis of variable regions encoding AB1 and gamma-type AB2antibodies from the NeuGc-containing ganglioside family

The variable regions from P3, a murine monoclonal antibody (MAb) against Ne uGc-containing gangliosides, and two anti-idiotype MAbs directed to P3 MAb were cloned and sequenced. Comparisons with previously reported sequences s howed that P3 is a germline antibody encoded by genes from the V(H)Q52 and V(kappa)19 families. Analysis of nucleotides at the heavy chain CDR3 (H-CDR 3) showed the presence of an extensive 3' N region that contains almost 50% of the nucleotides of this CDR. In addition, amino acid sequence analysis of the H-CDRs of this MAb revealed the presence of three arginines, two of which are present in the H-CDR3, that could be involved in the interaction of P3 MAb with its electronegative epitope on gangliosides. Anti-idiotype 1 E10, which seems to define a "regulatory" idiotope on P3 MAb (it induces Id + Ab3), represents a germline Ab2 that belongs to the V(H)J558 and V(kappa) 10 gene families. By contrary, the anti-idiotype 3B11 is an extensively mut ated antibody that belongs to the V(H)3660 and V(kappa)4/5 gene families, d efining a "private" idiotope on P3 MAb. Even when different V genes contrib ute to the variable regions of 1E10 and 3B11 MAbs, they share an acidic mot if E/D-D-Y/D-Y-DinH-CDR3, suggesting that both Ab2s recognize paratope posi tive residues on the Ab1. Therefore, complementary electrostatic interactio ns involving H-CDR3 from both Ab1 and Ab2, might provide a clue to understa nd the molecular basis for the generation of gamma -type anti-idiotype anti bodies to V regions recognizing glycolylated ganglioside antigens.