The Molecular Origin of Regulatory Idiotypes

Abstract

A complete immunochemical and molecular profile was generated for a group of hybridoma and myeloma antibodies bearing the A48 regulatory idiotype (RI). These A48 RI⁺ antibodies were derived from normal or idiotypically manipulated mice and were selected either for utilization of a V_HX24 V_H gene or expression of the A48 RI. Among the hybridomas selected for V_HX24 V_H utilization a variety of antibody specificities were seen with the fructosan specificity occurring least frequently and the N-acetylglucosamine specificity occurring most frequently. A variety of V_k families were used with a bias for the V_k1 family by the antibodies deriving from untreated mice The A48 RI was expressed by only 3 of these antibodies, none of which were fructan specific. Two used the canonical V_HX24-V_k10 combination utilized by the A48 and UPC 10 prototypes, and one used the V_HX24-V_k1 combination. This demonstration of A48 RI expression by non-fructan specific, non-V_HX24⁺ V_k10⁺ antibodies was extended by showing expression of this Id by two monoclonal antibodies specific for the Sm self-antigen, one rheumatoid factor and two monoclonal antibodies specific for influenza virus hemagglutinin molecule. They used different V_H-V_L combinations. Among the monoclonal antibodies selected for A48 RI expression all exhibited fructan binding activity and the vast majority used the V_HX24-V_k10 association. A collective analysis of the V_H and V, sequences of all these A48RI⁺ antibodies showed idiotype expression was not associated with any particular germline V_H or V_L gene, D, J_k or J_H sequence. Three positions on the light chain and one on the heavy chain were identified which could represent the structural correlates for the A48 regulatory idiotype.

Key Words:

• regulatory idiotype
• structural correlate
• antigen specificity
• V_H gene
• V_K gene