抗CEAモノクローナル抗体に対する抗イディオタイプモノクローナル抗体の解析

Five anti-idiotypic monoclonal antibodies (anti-Id MoAbs) were generated from a BALB/c mouse immunized with anti-CEA MoAb MA208 in a syngeneic system. These anti-Id MoAbs specifically reacted to MoAb MA208 and inhibited CEA-MoAb MA208 binding. These results indicate that all of these anti-Id MoAbs recognized private idiotopes at the paratope of MoAb MA208. Mouse sera, which had been immunized by these anti-Id MoAbs, were analyzed to test the reactivity with CEA. Two kinds of mouse sera (immunized with anti-Id MoAbs M7-625 and M7-914) showed reactivity to CEA by binding assay, Western blot analysis and competition assay. These results sug- gest that anti-Id MoAbs M7-625 and M7-914 bear an "internal image" of the MA208-defined epitope onCEA. Anti-anti-Id MoAbs against anti-Id MoAb M7-914 revealed a cross-reactive idiotope for anti-Id MoAb M7-914 and M7-413. An amino acid analysis of the heavy chain of anti-Id MoAb M7-625 was performed. The result- ing amino acid sequence was compared with that of CEA. Some homologies between these two molecules were recognized at certain portions of CDR2 and CDR3 of MoAb M7-625 and domain III of CEA