Generation of hybrid hybridomas secreting human IgM class hybrid antiricin and antidiphtheria toxin antibodies

Two lines of mouse-human hybridomas were fused to produce human bifunctional antibodies. A hybridoma that secretes human IgM (κ) class antiricin monoclonal antibody was treated with actinomycin D to inhibit cell growth. Another cell line, secreting human IgM (λ) class antidiphtheria toxin monoclonal antibody, was 6-thioguanine resistant (HAT sensitive). Six hybridomas secreting IgM with both κ and λ light chains were obtained. Two of them secreted antibodies with antiricin specificity (κ and λ light chains) and antidiphtheria toxin specificity (κ and λ light chains). Antidiphtheria toxin antibodies secreted from other hybrid hybridomas did not contain κ light chain, but λ chain. A hybrid hybridoma clone 5–29 secreted complete hybrid IgM with lowered affinity to diphtheria toxin. These results suggested unbalanced recombination of immunoglobulin polypeptide chains in hybrid hybridomas.