Spontaneous fusion between lymphoid and carcinoma cells in vivo has been described previously (e.g. 1). Splenocytes from mice treated with LPS or mitogen have been reported to fuse better with myeloma cells using PEG as fusion agent than splenocytes from untreated mice (2). We report a phenomenon where immunization of mice with formalin treated, whole Haemophilus paragallinarum bacteria induced spontaneous fusion of splenocytes with myeloma cells in vitro, without the aid of any fusion agent. Co-immunization of mice with H. paragallinarum and an unrelated antigen (hen's egg white lysozyme), followed by co-culturing of the immune splenocytes with SP2/0 myeloma cells, yielded stable hybridoma cell lines producing anti-lysozyme antibodies. H. paragallinarum may be used in adjuvants to simplify the production of monoclonal antibodies, and the discovery of a promotional activity of a gram negative bacterium on cell fusion and hybridoma formation may shed new light on spontaneous fusion as a natural immune phenomenon in cancer.
