Kinetics of monoclonal antibody production in low serum growth medium.

Factors affecting growth and monoclonal antibody production in vitro by a mouse-mouse hybridoma cell line have been investigated in a series of studies. The goal was to maximize antibody yields and demonstrate that antibodies can be produced efficiently on a large-scale in fermentors. This initial report describes (i) development of a radial immunodiffusion assay for accurate determination of antibody levels in culture, (ii) a culture medium formulation that allowed for reduction in the amount of fetal bovine serum required for good cell growth, and (iii) the kinetics of cell growth and monoclonal antibody production in low-serum media. The radial immunodiffusion assay, employing rabbit anti-mouse IgG antibodies in the immobile phase and the monoclonal antibody (an IgG2a to Rhizobium japonicum cells) as the antigen in the mobile phase, was more reproducible and reliable for determining antibody levels in culture broth than was an indirect enzyme-linked immunosorbent assay. Addition of 0.25% Primatone RL and 0.01% Pluronic F-68 to Dulbecco's modified Eagle medium allowed cells to adapt to growth in medium containing as little as 1% fetal bovine serum; without these additives, 5% serum was the lowest level attained. For the kinetic studies, cells were grown in the low-protein medium in 3 liter spinner flasks. Antibody production occurred during the growth phase, however, significant amounts were also produced during later phases when the cells had stopped growing. Final titers were 100-200 micrograms/ml. It was concluded that maintenance of cell viability is more important than growth rate in production of antibody. This conclusion, confirmed in other studies, has developed into the major underlying strategy employed in subsequent investigations to maximize antibody production in stirred reactors.