EFFECT OF ENDOGENOUS PROTEINS ON GROWTH AND ANTIBODY PRODUCTIVITY IN HYBRIDOMA BATCH CULTURES

It has been shown that some B-cell hybridomas secrete autocrine factor s in vitro which can influence cell metabolic processes. Rather than s creen specifically for suspected cytokines, that may or may not affect our cell line, we have examined the lumped effects of intracellular a nd secreted factors on cell proliferation and monoclonal productivity in hybridoma batch cultures. Firstly, supplements of total soluble int racellular proteins combined with other intracellular metabolites were found to both decrease the specific growth rate and increase the anti body production rate at higher concentrations in batch culture. This i s an important consideration in high cell density cultures, such as pe rfusion systems, where a reduction of growth by the presence of intrac ellular factors may be compensated by an increase in MAb production. I n addition, flow cytometry data revealed that the average eel cycle G( 1) phase fraction was unaffected by the variation in the maximum speci fic growth rates during the exponential growth phase, caused by the ad dition of intracellular factors; this suggests that higher MAb product ivity at lower growth rates are not a result of cell arrest in the G(1 ) phase. Secondly, secreted extracellular proteins larger than 10,000 Daltons, which were concentrated from spent culture supernatant, were shown to have no significant effect on growth and specific MAb product ivity when supplemented to batch culture at levels twice that encounte red late in normal batch culture. This indicates that endogenous secre ted cytokines, if at all present, do not play a major autocrine role f or this cell line.