Evaluation of interleukin-4 concentration by ELISA is influenced by the consumption of IL-4 by cultured cells.

The ability to accurately measure cytokine secretion by immune cells is critical to the evaluation of immune mechanisms in the context of Th1 and Th2 responses. In this study, we demonstrated that in vitro consumption of interleukin-4 (IL-4) by stimulated cells influences the concentration of IL-4 in the culture supernatant. In contrast, evaluation of IL-4-secreting cells by ELISPOT is not influenced by the consumption of IL-4 by cultured cells. These discrepancies influence the cytokine profile when responses are evaluated in relation to the secretion of other cytokines, for example, interferon-gamma (IFN-gamma). This information ultimately should enable investigators to evaluate immune responses accurately without concerns of bias resulting from in vitro consumption of IL-4, thus providing much more reliable interpretations of the type of immune response being evaluated.