Direct stimulation of cytokines (IL-1β, TNF-α, IL-6, IL-2, IFN-γ and GM-CSF) in whole blood. I. Comparison with isolated PBMC stimulation

Production of interleukin 1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), interleukin 2 (IL-2), interferon gamma (IFN-γ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) after stimulation by lipopolysaccharide (LPS) and phytohemagglutinin (PHA) was studied in 110 diluted whole blood (WB) culture and in peripheral blood mononuclear cell (PBMC) culture. Cytokines IL-1β, TNF-α and IL-6 are preferentially stimulated by LPS whereas IL-2, IFN-γ and GM-CSF are stimulated by PHA. Combination of 5 μg/ml PHA and 25 μg/ml LPS gave the most reliable production of the six cytokines studied. IL-1β, TNF-α and IL-6 represent a homogeneous group of early-produced cytokines positively correlated among themselves and with the number of monocytes in the culture (LeuM3). Furthermore, IL-1β was negatively correlated with the number of T8 lymphocytes. IL-2, IFN-γ and GM-CSF represent a group of late-produced cytokines. Kinetics and production levels of IL-6 and GM-CSF are similar in WB and PBMC cultures. In contrast, production levels of TNF-α and IFN-γ are higher in WB than in PBMC whereas production levels of IL-6 and IL-2 are lower in WB than in PBMC. Individual variation in response to PHA + LPS was always higher in PBMC cultures than in WB cultures. The capacity of cytokine production in relation to the number of mononuclear cells is higher in WB, or in PBMC having the same mononuclear cell concentration as WB, than in conventional cultures of concentrated PBMC (106/ml). Because it mimics the natural environment, diluted WB culture may be the most appropriate milieu in which to study cytokine production in vitro.