We compared serum and protein-free cultures of a ras-amplified recombinant
BHK-21 cell line (ras-rBHK-IgG), which hyperproduces a lung cancer specific
recombinant human monoclonal antibody. Ras-rBHK-IgG cells were shown to gr
ow well, even in protein-free medium and to be morphologically similar to c
ells cultured in serum containing medium. However, the growth rate of ras-r
BHK-IgG cells was considerably slower in protein-free medium, which results
in a longer maintenance period compared with cells cultured in serum conta
ining medium. In addition, it was found that antibody production in protein
-free culture had a ten times higher maximum than cells cultured in serum c
ontaining medium. On the other hand, in high density culture, using the hol
low fiber bioreactor system, ras-rBHK-IgG cells could be maintained for a m
onth in protein-free culture in contrast with serum culture, which only las
ted for half a month. However, the marked increase of antibody production w
as not observed. A total amount of about 15 mg of the recombinant antibody,
obtained in protein-free culture, was about two times of that obtained in
serum culture, and was shown to be reactive to lung cancer cells in tissue.
From these properties in protein-free medium, it is concluded that protein
-free culture of ras-rBHK-IgG cells is suitable for middle scale production
of recombinant human monoclonal antibody.