DEVELOPMENT AND EVALUATION OF THE SPECIFICITY OF A RAT MONOCLONAL ANTIIDIOTYPE ANTIBODY, WN, TO AN ANTI-B-CELL LYMPHOMA MONOCLONAL-ANTIBODY, LL2

Anti-idiotype monoclonal antibodies (Mabs) to mLL2, an anti-B-cell lym phoma and CD22-specific murine IgG2a-kappa Mab, were generated by hybr idoma technology from splenocytes of Copenhagen rats immunized with mL L2 F(ab')(2). Mab WN, an IgGZa-kappa, was selected based on its specif ic binding to mLL2 and not other IgG isotypes or anti-B-cell Mabs, In a radioimmunoassay, WN was found to inhibit the binding of I-125-label ed mLL2 to Raji cells and to have no effect on the binding of other B- cell-reactive antibodies, Using high performance liquid chromatography analysis, WN was shown to complex specifically with both mLL2 and mLL 2 Fab'. Meanwhile, we have constructed chimeric (cLL2) and humanized ( hLL2) versions of LL2. Both cLL2 and hLL2 were demonstrated to retain the original antigen specificity and affinity of mLL2 [S. O. Leung et al., Proc. Am. Assoc. Cancer Res., 2872 (abstract), 34: 481, 1993]. Th e specific binding of WN to either radioiodinated or peroxidase-conjug ated mLL2 was inhibited in a dose-response manner, and to a similar ex tent by mLL2, cLL2, and hLL2. Since the mLL2 complementarity-determini ng regions are the only sequences common to mLL2, cLL2, and hLL2, the result confirms that WN is specific to the antigen-binding complementa rity-determining regions. A WN binding assay is currently being evalua ted as a substitute for the tedious, and sometimes inconsistent, Raji cell-binding assay for the determination of LL2 immunoreactivity. In c onclusion, we have developed an anti-idiotype Mab, WN, to mLL2. Its po tential use as a surrogate antigen for B-cell lymphoma is under invest igation.