Instability of a hybridoma cell line in a homogeneous continuous perfusion culture system.

In this study several analytical techniques were applied to obtain information about the stability of expression, the yield, and the integrity of a monoclonal antibody (Mab) produced by hybridoma cell line RIV6 in a homogeneous continuous perfusion culture system. The total antibody as well as the isotype-specific antibody contents decreased continuously during the course of cultivation, while the viable cell concentration remained constant. The origin of the discrepancy between the Mab contents observed by two enzyme-linked immuno sorbent assay (ELISA) systems during the steady state was due to fragmentation of the IgG molecule, either cytoplasmic or in the culture fluid, as determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting. The IgG-secreting cells as well as the fraction of cells containing a high cytoplasmic IgG content decreased continuously during cultivation. The isoelectric focusing (IEF) pattern showed the appearance of two additional bands after five days of cultivation. This work indicates that cell line RIV6 is unstable in the culture system used, with respect to cell properties and product formation.