Fusion

The two most common approaches to generate B cell:myeloma hybrids are either polyethylene glycol (PEG)-mediated fusion or electrofusion.  Introducing PEG into a mixture of B cells and myeloma cells causes aggregation of cells and aggregation of membrane proteins, the latter leading to large patches of bare homogenous lipid membrane bilayer.  PEG treatment fosters close bilayer-bilayer membrane contacts (0.5 nm gap) between the target cells, enabling membrane fusion.  Some cells are resistant to PEG-induced aggregation of membrane proteins; without these large bare patches of membrane, fusion efficiency is greatly diminished.  In contrast, electrofusion utilizes physical rather than chemical methods to achieve cell:cell fusion.   An electric field (AC waveform) is applied to a mixture of B cells and myeloma cells, which polarizes the cells and induces their linear alignment in tight ‘pearl chain’ structures (15-25 nm aqueous gap between cells).  A DC waveform pulse is then applied to induce cell fusion.  This is followed by application of an AC electric field to hold fused cells together to promote membrane stabilization.  In most head-to-head comparisons, the literature indicates that electrofusion is 2-10x more efficient in inducing hybridoma formation than PEG.