β‐Cyclodextrin as a substitute for fetal calf serum in the primary antibody response in vitro

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Abstract
Fetal calf serum (FCS) must be present at 10% in the culture medium for optimally eliciting the primary antibody response to sheep erythrocytes (SRBC) in murine lymphocytes. The response was no longer observed when FCS was reduced to less than 1%. However, we found that the addition of 250–500 μg/ml β‐cyclodextrin (β‐CD) to RPMI 1640 medium containing 1% FCS restored the immune response to a level comparable to that observed in 10% FCS‐containing medium. β‐CD did not further augment the response in the presence of 10% FCS. The order of effectiveness of various cyclodextrin compounds tested was as follows: β‐CD (100) > α‐CD(30) > γ‐CD(10) > heptakis (2,6‐O‐dimethyl)β‐CD (< 1). The in vitro antibody response varied drastically depending on the lot of FCS added to the culture medium. The important observation was that even a deficient lot of FCS could elicit the antibody response as efficiently as a good lot if it was added to the culture medium at 1% in combination with β‐CD, β‐CD was also effective in inducing the primary antibody responses to both SRBC and dinitrophenylated Ficoll in serum‐free RPMI 1640 medium containing bovine serum albumin, insulin and transferrin. In serum‐free conditions, the responses were 40–50% of those in serum‐containing medium. β‐CD did not increase the number of antibody‐forming cells nonspecifically, nor did it show a significant mitogenic activity and cytotoxicity. These data suggest that β‐CD is a useful material as a serum substitute in inducing primary antibody response in vitro.