Regulation of the in vitro secondary antibody response: I. Suppression by relatively high,but physiological levels of calcium ion

Secondary antibody responses generated in vitro with spleen cells from mice primed and boosted with SRBC or TNP-KLH antigen were found to be influenced by the amount of Ca²⁺ in the culture medium. Relatively low levels of Ca²⁺ (0.1 mM) were optimally supportive for the generation of PFC in vitro, with higher, more physiological levels of Ca²⁺ (1.0–1.7 mM) suppressing the generation of PFC by as much as 100%. Suppression by high levels of Ca²⁺ was most pronounced when the amount of antigen used to elicit the in vitro antibody response was high, whereas responses generated by lesser amounts of antigen were minimally affected by Ca²⁺ level. Ca²⁺-mediated suppression was localized to an intermediate phase (24–48 hr) of the response. Mitogenic and polyclonal antibody responses were not affected by high levels of Ca²⁺. The effect of Ca²⁺ concentration on the secondary, IgG-producing antibody response may be significant in terms of understanding the various control mechanisms interacting in regulation of IgG synthesis.