Characterization of a unique anti-DNA hybridoma

We have previously described the isolation and in vitro binding properties of eight anti-DNA monoclonal antibodies (MAbs) from an MRL-lpr mouse. In light of recent reports that have indicated it is possible to isolate multiple MAbs from a single hybridoma, our pathogenic hybridoma, 11F8, was examined for evidence of similar phenomena. Chromosome counting suggested that 11F8 cells are unusual and might indeed be expressing multiple heavy and/or light chains. PCR, cloning, and sequencing of immunoglobulin heavy and light chains indicate that 11F8 displays expression of both gamma 2a and gamma 3 heavy chains at the DNA level. Flow cytometry and amino acid sequencing reveals that expression of multiple isotypes also occurs at the protein level but only a single heavy- and light-chain sequence is able to bind DNA. Based on these results, we conclude that 11F8 is an unusual hybridoma that secretes two distinct heavy and at least one light chain from a single cell, and may represent a trioma, a stable three-cell fusion.