Isolation of immunoglobulin class switch variants from hybridoma lines secreting anti-idiotope antibodies by sequential sublining.

The combination of a sensitive radioimmunoassay with a simple limiting dilution approach designated as sequential sublining (ssl) allowed us to isolate spontaneous class switch variants from two hybridoma lines secreting monoclonal anti-idiotope antibodies against a germ-line encoded antibody with defined hapten-binding specificity. We obtained two families of antibodies, one of which consists of IgG1, IgG2b, and IgG2a, the other consisting of IgG1, IgG2b, IgG2a, and IgE antibodies. The members of a family possess identical anti-idiotypic specificity. We describe serologic and biochemical properties of the class switch variants as well as the frequency and order of "forward" and "reverse" switching, and we compare the ssl approach to other related methods. The ssl allows the rapid isolation of somatic mutants, which have acquired a new predefined antigenic determinant, without complicated equipment and even when the frequency of the mutants is as low as 10(-6) or 10(-7).