An idiotypic marker for the VL region of an homogeneous antibody.

Studies on the inheritance of idiotypes in rabbits have not yielded consistently positive results. This inconsistency may be due to the fact that an idiotype is a complex phenotype, dependent in most cases on the coordinate expression of unlinked H and L chain genes. In an attempt to reduce this complexity, H and L chain specific idiotypes have been sought. In one fortuitous instance, an homologous antiidiotypic serum raised against homogeneous antistreptococcal antibody 4539 was shown to bind free 4539 L chain. An anti-idiotypic antibody fraction specific for the L chain was isolated from this antiserum by affinity chromatography on a column to which 4539 L chains had been covalently bound. The specificity of this preparation was demonstrated by radioimmunoassay, and sera from both related and unrelated rabbits were screened for the presence of the L chain idiotype. Positive tests were obtained for sera from 56% of related rabbits immunized with group C streptococci, while preimmune sera and group C and group A antisera from unrelated rabbits had no detectable levels of the 4539 L chain idiotype. The 4539 L chain also expressed a recently described, genetically determined CL marker (b4var). This combination of markers will allow CL-VL linkage studies. More recently a procedure specifically designed to elicit chain-specific idiotypic antisera has been successfully tested, yielding an antiserum specific for the H chain of another antistreptococcal antibody, 4135.