Monoclonal antibodies against tumour-associated antigens: mycoplasma as a major technical obstacle and its possible circumvention by azaserine selection medium.

: In experiments aimed at generating monoclonal antibodies against tumour associated antigens, mice are usually immunized with cancer cells (or membrane fractions prepared from it) obtained from surgery or cultured in vitro. In both situations there is the danger of introducing mycoplasmas into the hybridoma cultures even if the myeloma cell line and the mice used for immunization or feeder cell preparation are not infected. Mycoplasmas kill hybridoma cells during HAT selection because they excessively degrade thymidine. The use of azaserine instead of aminopterin in hybrid selection circumvents the necessity for thymidine and therefore may allow survival and growth of hybridomas in the presence of mycoplasmas.