Idiotype expression in rheumatoid synovial plasma cells

The majority of the polyclonal plasma cells identified in the synovial tissues of rheumatoid arthritis patients contain immunoglobulins that express a common idiotype related to that of the monoclonal cryoglobulins of the Wa group (RCRI). In these same tissues, there are twice as many plasma cells which are marked by a common idiotype yet do not show binding of aggregated IgG. These plasma cells are members of an idiotypically parallel set relative to those which produce rheumatoid factor. Direct comparison of rabbit polyclonal RCRI+ plasma cells with murine monoclonal RCRI+ plasma cells using two color fluorescent counterstains shows that the epitope recognized by the monoclonal anti-RCRI exists among a set of epitopes present in the RCRI. Since all the monoclonal RCRI+ plasma cells are not also positive with the polyclonal anti-RCRI antisera, the epitope characterized by the monoclonal antibody Glo 86.3 is not included among the set of epitopes the polyclonal antiserum identifies. A suitably absorbed anti-idiotypic polyclonal antiserum is superior to monoclonal antibodies for the purpose of detection of molecules (and cells) that are part of a polyclonal reaction involved in a given immune response.