Idiotypic Multireactivity of ‘Natural’ Antibodies

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Abstract
One hundred and twenty IgM‐secreting hybridomas derived from unmanipulated 6‐day‐old BALB/c mice were screened for reactivity with the prototype idiotypic and anti‐idiotypic monoclonal antibodies, defining three well established systems, namely TEPC 15:10/13–15, J558:CD3.2, and MOPC 460:F6(51). Up to 25% of all IgM antibodies reacted with at least one of the six specific ligands, half of the latter being ‘monospecific’, the others reacting with two or more aniibodies. A detailed analysis of the four most multi‐reactive clones showed individually specific patterns of reactivity and revealed reactions of the same IgM molecule in idiotypic systems previously studied independently. Furthermore, when tested for functional interactions with syngeneic helper T cells expressing MOPC 460‐like clonotypes, one of these antibodies was found to inhibit effector helper activity. The results show the existence of ‘natural antibodies’ with idiotypic reactivities related to recurrent clonotypes in the strain. They may be either ‘specific’ or ‘mullireactive’, and might connect idiotypes on T and B cells and on antigenic systems so far studied independently.