Modulatory effects of β-endorphin on interferon-γ production by cultured peripheral blood mononuclear cells: Heterogeneity among donors and the influence of culture medium

The stress-responsive neuropeptide β-endorphin (β-END) has been shown to either enhance or suppress interferon-γ (IFN-γ) production by mitogen stimulated peripheral blood mononuclear cells (PBMNC) in vitro. In this study, we investigated whether donor selection and the medium used for cell culture influenced the modulatory effect of β-END on the IFN-γ production by PBMNC. Considerable variation of the effect of β-END on IFN-γ production was observed in individuals who underwent multiple testing. Suppression of IFN-γ was significantly greater in 16 male donors (29 ± 6.0%) compared to 8 female donors (1.5 ± 6.4%) when PBMNC were preincubated for 3 h with β-END followed by concanavalin A stimulation for 72 h in medium containing 20% fetal bovine serum (FBS). Lowering the concentration of FBS resulted in enhanced production of IFN-γ by PBMNC exposed to β-END. Arachidonic acid or β-END added separately to medium containing 3% autologous serum produced no suppression of IFN-γ, but when added together resulted in significant suppression. This observation provides support for the hypothesis that β-END achieves its suppressive effect on IFN-γ via a mechanism involving arachidonic acid metabolism. We conclude that the modulatory effect of β-END on IFN-γ production by PBMNC is both donor and medium dependent.