THE REQUIREMENT FOR HYDROCORTISONE IN ANTIBODY-FORMING TISSUE CULTIVATED IN SERUM-FREE MEDIUM

It was previously reported from this laboratory that the secondary antibody response can regularly be elicited in vitro from fragments of rabbit lymph node node cultured in Eagle's medium supplemented with normal rabbit serum. Evidence is now presented that physiological levels of hydrocortisone (0.01 to 1.0 µM) can substitute for serum in the culture medium. However, with the omission of serum, serine (0.1 mM) must be included among Eagle's "essential" amino acids for consistent optimal antibody production. In some experiments the addition of insulin (0.5 unit/ml) and vitamin B₁₂ (0.5 µg/ml) has further enhanced the secondary response in this serum-free medium.