Continuous antibody production by phytohemagglutinin-L-aggregated hybridoma cells

Abstract

Phytohemagglutinin-L (PHA-L) induced aggregation of SP2 myeloma and antibody-producing hybridoma cells. The aggregates were of diverse shapes, and major-axis length of the hybridoma aggregates was mostly 50–80 μm at 1 μg/ml PHA-L and 100–150 μm at 5 μg/ml. PHA-L did not suppress growth rate at these concentrations. The aggregated cells had almost the same antibody productivity as that of non-aggregated cells in a static culture. Essentially, identical results were obtained with soybean agglutinin (SBA). On the other hand, pokeweed mitogen (PWM) did not induce apparent aggregation at a concentration of 10 μg/ml. These results suggest that lectin binding to particular carbohydrate moiety on the cell surface is necessary for cell agglutination. Using PHA-L, a 200-ml suspension culture of aggregated hybridoma cells was successfully performed in a spinner flask over 10 days. The aggregates were mainly globular with a diameter of 50–100 μm at 1–2 μg/ml PHA-L. The aggregation greatly enhanced settlement of hybridoma cells by gravity, and medium exchanges were thereby easily performed in a short period. During a course of the semi-continuous culture, antibody concentrations of culture medium were maintained at approximately 10 μg/ml which was comparable to that of static culture of the aggregated hybridoma cells. Thus, the lectin aggregation is applicable to the separation of culture medium from anchorage-independent cells like hybridomas, and can be employed in a large-scale commercial production of biologically active proteins.