Idiotypic analysis of potential and available repertoires in the arsonate system.

We have shown that, by suitable idiotypic manipulation, BALB/c mice can express the major cross-reactive idiotype (CRI) of A/J mice in response to azophenylarsonate (Ars). In order to know if the CRIA idiotype is present in the potential repertoire of BALB/c before any intentional selection, we used polyclonal activation in vitro and limiting dilution analysis. The readout was done with two monoclonal anti-CRIA antibodies that recognize distinct idiotopes on a CRIA+ A/J germline-encoded monoclonal antibody. We studied the frequency of CRIA+ lipopolysaccharide (LPS)-reactive cells in the spleens of nonimmune and immune A/J mice and in the spleens of naive and manipulated (i.e., producing CRIA+ antibodies) BALB/c mice. A/J and BALB/c naive individuals presented very high frequencies of Ars-specific B cells while the frequency of CRIA+ B cells was only a minor subset (0.5%) of the total Ars-specific subset in the two strains. When A/J mice were immunized with Ars-keyhole limpet hemocyanin, a clear preferential expansion of the CRIA+ minor subset of A/J mice was observed (100x). No such enhancement was observed in BALB/c mice similarly treated. Manipulated BALB/c mice presented a higher frequency of CRIA+ anti-Ars B cells than naive or antigen-immunized BALB/c individuals.