Immunization of rabbits with anti-VHa allotype antibody leads to the production of an "anti-cross-reactive idiotype (IdX)" reagent which appears to recognize a highly conserved IdX on anti-allotype antibodies. In many rabbits, a large percentage of this "anti-IdX" reagent does not express the nominal VHa framework allotype of the rabbit from which it was derived and is otherwise serologically indistinguishable from the original antigen, i.e. a1 or a2 allotype. To determine whether these anti-IdX molecules were in fact anti-IdX (or internal images) or were induced immunoglobulins bearing latent VHa allotypes, immunoelectron microscopic analysis of the molecules in complex with Fab anti-allotype antibody was conducted. The results show that the complexes do not resemble idiotype-anti-idiotype interactions but are essentially indistinguishable from allotype-anti-allotype complexes. We conclude that a major component of the "anti-idiotype" response of these anti-VHa-immunized rabbits is the production of Ig molecules bearing latent VHa allotypes.

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Previously, we induced Ab to a common idiotypic specificity (IdC) of rabbit anti-a2 VH Ab. We observed then that some of the putative anti-IdC Ab molecules induced by immunizing a1a1 rabbits with anti-a2 Ab did not have the expected nominal allotypic markers (a1, x32, or y33) characteristic of the genotype of the immunized rabbits. Thus, immunization of a1 a1 rabbits with a1 anti-a2 Ab induced population of molecules that reacted with anti-a2 Ab but bore an unidentified (unknown) VH region marker. The following observations indicate that these molecules bear a "latent a2" allotypic marker: (a) when the unknown VH molecules were used to immunize a1 a1 and a3 a3 rabbits, anti-a2 Ab was produced; (b) when an a2 a2 rabbit was immunized with the same preparation of unknown VH molecules, an anti-idiotypic Ab was produced; and (c) when the unknown VH molecules were used to inhibit the binding of labeled a2 IgG to anti-a2 Ab, the inhibition curve obtained was essentially the same as that obtained by using normal a2 IgG. Thus, immunization of a1 a1 rabbits with a1 anti-a2 Ab provided a bidirectional stimulus to produce both nominal "a1" anti-IdC Ab and a "latent a2" allotype. The distribution of nominal to latent allotypes induced ranged from 3% nominal/92% latent to 57% nominal/23% latent. In absolute terms, the maximum amount of "latent a2" molecules was 1.18 mg/ml of serum, which far exceeds the amount of latent allotype described by others (0.3 mg/ml of serum). The effective induction of large amounts of "latent a2" allotype may have resulted from a simultaneous stimulation of an idiotope and a paratope on the surface of the "latent a2"-producing cells.

No abstract

We have shown that after immunization of homozygous a1 rabbits of the B immunoglobulin (Ig) heavy chain haplotype with anti-a2 antibody (Ab) a population of molecules appears that has all of the serologic characteristics of the a2 allotype. We have now isolated these putative latent a2 molecules, have separated the heavy chains, and after enzymatic deblocking, have determined the first 19 N-terminal amino acids. For all eight allotype-associated residues, these putative latent a2 molecules have the amino acid residues typical of a2 allotype. As expected, the preimmune IgG from this a1a1 rabbit has the amino acids typical of the a1 allotype. Thus by partial amino acid sequence analysis, we provide additional evidence that the latent a2 allotype can be induced in a1a1 rabbits of the B heavy chain haplotype by immunization with anti-a2 Ab. Rabbits of other heavy chain haplotypes were also immunized with anti-a2 Ab and were tested for their ability to synthesize latent a2 allotype. Thus far, a1a1 rabbits of the A, B, C, and I heavy chain haplotypes all synthesize latent a2 allotype. In contrast, a3a3 rabbits of the G and H heavy chain haplotypes did not synthesize latent a2 allotype.