Influence of serum on zinc, toxic shock syndrome toxin-1, and lipopolysaccharide-induced production of IFN-gamma and IL-1 beta by human mononuclear cells.

Measurement of cytokine secretion in vitro is usually performed in culture medium supplemented with human serum. We compared the secretion of interferon-gamma and interleukin-1 beta as a parameter for lymphocyte and monocyte activation in RPMI 1640 medium supplemented with fetal calf or autologous serum in serum-free medium and protein-free medium. Four different stimulatory mechanisms were tested: phytohemagglutinin, toxic shock syndrome toxin-1 (TSST-1), lipopolysaccharide (LPS), and zinc ions. We found that the optimal stimulatory zinc concentration depended on the total protein content of the medium, whereas the monokine levels were dependent on the concentration of transport proteins such as transferrin. Monokine induction by LPS or TSST-1 were each influenced by the protein and serum composition in a specific manner. Our results show that the differing mechanisms of cytokine induction are influenced by the medium and serum composition in a diverse but specific manner. Serum- or protein-free medium are especially suitable after superantigen challenge when LPS activity needs to be ruled out or after activation by agents with only a weak stimulatory capacity.