Regulation of the response to alpha(1-3) dextran: an anti-dextran associated idiotope of BALB/c mice is also expressed on A/J anti-NIP antibodies.

The functional properties of a mAb reactive to the B5 idiotope were analyzed in BALB/c, A/J and C.B20 mice. the B5 idiotope was specifically associated with the alpha(1-3) DEX response in a strain-specific manner in BALB/c mice (responder strain). It was serologically distinct from the previously described IdX idiotype and overlapped on part of the IdX+ and IdX- BALB/c anti-alpha(1-3) DEX response. While treatment of adult BALB/c mice with mAb B5 enhanced the serum anti-alpha(1-3) DEX antibody synthesis and induced de novo antibody synthesis in non-responder C.B20 mice, A/J non-responder mice remained unresponsive, despite elevated levels of serum B5+ dextran non-binding Ab3 immunoglobulins. However, in some of these A/J mice, we detected an enhancement of anti-NIP antibody synthesis. This anti-NIP antibody component was (1) specifically induced by mAb B5, (2) found in A/J, but not in BALB/c or C.B20 mice, and (3) specific towards the NIP hapten. These A/J anti-NIP antibodies bore either the lambda 1 or the kappa light chain and some of them also expressed the B5 idiotope. The B5 id thus appears as a typical id determinant shared by antibodies having different binding specificities, and it may have a role in the regulation of these responses.